Thanks to this message board we (2 adults an a 11 year old girl) are making good progress on planning our August trip to Costa Rica (I know, I like to plan early).
So far, we plan to spend two nights in Tortuguero and five nights near Manuel Antonio. That leaves us with 4 more nights and we don't quite know what to do with them. We would prefer to spend all 4 nights in the same place to cut down on travel time but we're not wedded to that. We are thinking about Playa Tamarindo or another Guancastle beach town but wonder if this will be "redundant" in terms of being at another beach location along with Manuel Antonio. Another thought is Arenal but we worry about having enough to do. The Osa Penisula seems a little too isolated and expensive for our tastes.
We did plan on spending one of the days in Manuel Antonio rafting the Savegre River but maybe we should instead take a one day trip out of San Jose on the Reventazon or Sarapiqui and then go somewhere for three nights.
Choices Choices Choices.
Any feedback on these thoughts would greatly be appreciated.

Do you need to spend any of those remaining 4 nights near San Jose because of your flight times?

I think that Arenal may be a good option but I find that 2 nights there are sufficient which would potentially leave you with 2 more nights. Our daughter always enjoyed the visits to the Tabacon hot springs and there are other attractions in the area as well (Hanging Bridges, canopy tours, waterfalls). We visited Arenal twice in August and really were not that lucky with the weather (we did not even glimpse the volcano during our first visit).

I hesitate to recommend Tamarindo any more since it has become really busy and built up in the last couple of years. Maybe a place like Samara or Malpais would suit you better. They are both different than Manuel Antonio (you are more likely to find a place directly on the beach, which I always enjoy). We enjoyed Manuel Antonio but found it quite busy, so a place like Samara or Malpais may be a good place to relax for a few days. Samara is easy to get to, Malpais is more difficult.
Another option would be a place in the Central Valley or the surrounding mountains from where you can do some day trips.

Give us some more information on your interests and I am sure you'll get more recommendations.

I am making my 8th trip to CR in late July or early August with my 10 year old niece. I always make time for Manuel Antonio, but I think 3-4 nights
there is plenty. Since you are alredy going to Tortuguero, I would suggest dividing the rest of your time between Arenal and the Central Valley. We are spending 2 nights near Arenal and taking the Cano Negro boat trip and also doing the Hanging Bridges tour. You can easily spend another half day at Tabacon Hot Springs. Near San Jose and the Central Valley, I would recommend La Paz Waterfall gardens, Sarchi, Zoo Ave, and if you like museums the Gold Museum, or the Jade Museum.

Greetings

Sounds like you're planning a trip remarkably similar to the one we did last August with our two 14 year old girls. Our trip in a nutshell:

Tortaguero 2 nights (fly in and fly out....saves time...do the canal tours...make reservations ahead for night-time turtle nesting tour....stay at Tortuga Lodge....Tortaguerro is wonderful)

Arenal Lodge 2 nights (drove up from SJ, fun....horseback to La Fortuna waterfall...found an off-the-beaten path hot springs....ate at El Novillo)

Villa blanca 1 night (to break up drive to Manuel Antonio...owned by ex-pres of CR...casitas....nice cloud forest experience) about 2 hours south of Arenal

Drive to Manuel Antonio (see crocodiles, stop at Villa Caletas for lunch)

Manuel Antonio 5 nights (green season special at Si Como No...your daughter will love the place...lots to do in area...we also did the Savegre and loved it...canopy safari...the national park...the butterfly garden...the beaches)

Overall, we like doing Tortaguerro first because we flew right down into real jungle. The Lodge is wonderful, with a cool pool next to the canal, great food, fun architecture, great hosts. The turtle-watching is a lifetime memory. We did Si Como No last as a splurge and it has more amenities (pool slide, theater, swim up bar, AC). In all we saw four different habitats, both coasts, as variety of food, many kinds of tours, many kinds of people....good variety. The Savegre is clean, beautiful, and no crocs.

Jim

Have fun!

There is another area that is pretty cool and seldom mentioned. It is in Guanacaste (north of Liberia)--the Rincon de la Vieja. It is a tropical dry forest--very beautiful there with an active volcano. We stayed at one of the resorts in the Golfo de Papagayo for a few days (north of Tamarindo an hour or so) and took a couple of tours into that area. Our three kids (who were late teens and early 20's) loved it there. We did a day of horseback riding at Los Inocentes (a ranch hotel near the Nicaraguan border)--a wonderful guided tour of the forest on horseback. .great lunch at the lodge. Another day we went to the same area but not so far north to Buena Vista Lodge for hot mud baths, a canopy tour, a cool water slide down the side of the mountain (quite a rush--you get in a big empty water slide built into the mountain with a big reservoir of water behind it (mountain water is cold in Costa Rica, too!). The operator pushed down on a big wooden lever, opens a door in the reservoir and the icy water literally flushes you down starting at about 50mph! It was awesome! And long. . .the rush lasted quite a while! The mud pots were cool, you put it all over you (sometimes you have lots of help as our 18 year old daughter found out)--swimsuit on, of course, let it dry, then shower it off (supposed to be quite therapeutic). . .then off you go to a series of different temp soaking tubs. . .from hot to cold. . .a lot of fun. .also a wonderful lunch. This day also included an excellent canopy tour--a must do while you are there!
Considering your daughter is 11, and you are already doing Manuel Antonio, I, too, think I would skip Tamarindo. . it is something of a party town. It can be a lot of fun, but probably not your best option. Malpais will be really slow paced, I believe, as will Samara be in August. The Osa is definitely for a time when you can just go there for your entire trip and not combine with anything else (my opinion) because it is so expensive! It is quite a little world unto itself. Arenal always a good option although chances of seeing the volcano in August are slim, the Tabacon Springs are pretty cool.

But then, as others have said, the central valley holds some real treasures. Poas Volcano (and Irazu Volcano) are both great day trips. The area up around Poas (including over toward La Paz Waterfall Gardens) is lovely, and the area to the southeast down around Irazu is beautiful as well. All the way down to Orosi, the valley, or over to Turrialba. Need to get an early start on the day for either volcano tour--and you will have a better chance of seeing. . .should be on top by 9:00 or so at least. This isn't a problem. You can drive from San Jose to either in an hour. San Jose is definitely worth a day of your time. . .and the little towns around like Sarchi and Heredia are just lovely. Sarchi is a really fun place to shop for souvenirs. You'd probably enjoy the Cafe Britt morning tour, and I would highly, highly recommend the 11 hour Highlights of Costa Rica tour. It includes: breakfast at a coffee farm, Poas Volcano and a little hike near there, a roadside stop at a hummingbird place overlooking a beautiful valley, lunch at Selva Verde, a jungle boat cruise on the Sarapiqui, a little time in Puerto Viejo de Sarapiqui, and a drive back to town through Braulio Carillo Parque Nacional. I went on this one alone once (in a tour group of 15) and had a great time. It just packs a really neat area of the country in on a loop north of San Jose. SO, you have all kinds of great things to choose from. . .ANY of them are going to be pleasing to you, I think! You'll want to go back later and do the other stuff that you missed this time!

For those of you who have been to these areas in August (especially the North Pacific region), how was the weather? Much rain?

Not much. Brief and usually light afternoon showers. Refreshing! Rain is not a problem in this area until September or October when it does tend to rain more. August should be just fine.