Monteverde cloud forest is a must see if you are in arenal. Hire a private guide and take a hike in the cloud forest... Zip lining is best in Monteverde IMO...

I think it looks nice. What's the snake museum?

Monteverde is a slight haul, even from Arenal, though it appears close on a map. You would need to allot extra time for this.

Other than that, it looks great. Do you know the age requirements for horseback-riding and ziplines?

6 and 3.75 ? You cant ride a horse TO the falls. You still have to walk down and UP a zillion steps.These aren't steps you're use to seeing. Each are a different height and width and climbing some you need to pull your knee up to your chin.
La Carolina is great(one of my faves) but don't expect corn flakes and pop tarts. The kids willing to sit down to beans rice and fried plantains at breakfast ? The Rio Celeste hike is pretty tough too.
Alaskan kids are 5 times tougher than their chubby little counterparts to the south but I still don't recommend taking kids under 13-14 to Costa Rica.One thing CR is NOT is child friendly.

Wow - is that true, Arenal botanical? Shillmac and others with small kids or grandkids have talked about CR as being kid-friendly (though of course there are specific age requirements for certain activities), and we've encountered many, many happy families with children under thirteen or fourteen. It would be interesting to hear the perpective of those who travel with children.

"CR is NOT...child friendly"
I feel so sorry for all those poor children in Costa Rica!

Of course, many adult activities are not appropriate for children, or allowed; but the Hanging Bridges (there are a couple) would be a good substitute for a more strenuous hike. A Cano Negro trip would be fun, and Los Laureles hot springs are an inexpensive and family friendly alternative to TAbacon.
Beaches are always nice for kids (but choose a gentle beach, not a surf beach).
YOu don't need to go on nothing but organized "fun" activities (those get expensive, too); exploring the scenery and short walks are very rewarding. (Take a short drive to Muelle, and see the iguanas in the trees; Google Muelle for nearby nature preserve/tours/ etc.)

Thank you everyone for your thoughts. Swanner, my husband and I actually visited Monteverde on our 1st trip to CR, (and did the yes, outstanding zip-lining on that trip), however due to age restrictions our children wouldn't be able to take part, thus the decision to skip Monteverde this time, and instead include zip-lining in Samara where they can participate.

Volcanogirl, the snake museum (or serpenteria) is wonderful! It was one of our favorite (and cheapest) places on a previous visit. Owned by a very nice young man who shared his love and knowledge of snakes, frogs, and other Costa Rican animals freely (many of which we were able to hold). After much googling we were able again to find them on Facebook, and it seems they have definitely expanded (perhaps a change of ownership?). Hopefully we'll be able to find what we loved to be the same.

I am thinking that we will probably forgo the horseback ride to the falls since we will be doing the ride at La Carolina (where in either instance our youngest would ride with us or the guide).

Arenalbotanical, maybe I should have a disclosure that we maybe have always bucked the system when it comes to traveling with our kids. At 5 months, and 8 months respectively we were tent camping with our daughters, at 6 months old we took our daughter to Alaska, and have continued traveling as such. They are not at all chubby, and have never in their life ever eaten a pop tart. Rather things like cous-cous, naan, tzatziki, and other "non-traditional" foods are part of their vocabulary. I think we're up for the challenge, although we like to think of it as an adventure.

sylvia3, I think our posts were in sync with each other. Thank you for your suggestions. I'll start googling on some of them now.

Congrats on scoring tickets, and happy anniversary! I'm sure you'll have a wonderful time; as you know, children are very adaptable and enjoy and remember simple things as well as organized fun. It's nice that you can provide special family memories for them.

Well-put,sylvia. And what better spot than CR! I often wish I'd brought my son when he was very young. All he'd have needed were his inate child-like curiosity and maybe a camera, and he would have been in heaven.

oh, yes, Cattail, that's a great idea for kids these days! With cheap digital cameras, they'll have a blast.

Costa Rica is definitively child friendly, both as a safe country and even more as a country where kids should never be bored. As I have been to same places you will go here are some remarks:
In La Fortuna no need to have a horseback riding to the waterfall; you can do this or afternoon on day of your arrival, or before hot springs. Instead do the Cano Negro boat tour (whole day) or ziplining with Hanging bridges.
La Carolina is a special place. You will love it, and kids also, even if there is no TV etc. Horseback riding at its best!!! Rio Celeste hike is a strenuous one; if previous day (or night) will rain hard then skip it. Rio Celeste will not be celeste, and trails will be muddy and slippery. Food at La Carolina is local but gooood.
Driving to Samara will take a little longer; we started at 10 am, arrived at Canas (do check Las Pumas while there) at 11 am, and after an hour continued to Samara where we arrived at 3 pm. So it was just short of 4 hours, with another 30 min lunch break between Nosara and Samara.
While in Samara do visit nearby Playa Carillo; its plam fringed white sand beach is one of better in Costa Rica, and also relatively safe for some bodyboarding.
Monteverde is another great location yet not feasible inside your itinerary; maybe next time?

We brought our 2 girls to CR when they were 8 and 12 and they loved it! We horseback rode to a waterfall (yes, had to get off and walk down steep incline the last bit), did hanging bridges at Arenal and they did zipline. We also did hot springs (at Los Lagos where we stayed) and did several days at Manuel Antonio. It was a great trip and wonderful for kids!

Not child friendly? Absolutely it is! I have such sweet memories of our 6 month old granddaughter at Monteverde and our 5 month old grandson in a small soda in Tuis-- the wait staff took them, held them, showed them things in the restaurant. Costa Ricans love children, and there are plenty of things you can do with them. Our oldest granddaughter even ziplined at the age of 4. She had a blast.

You sound like you have a good deal of experience traveling with children and doing unique things. Go for it!! Your itinerary sounds good. Plan on those transfers taking 1-2 hours more than you allowed. Have a great time!!

Thank you all for your thoughtful replies (and more accurate time estimates of travel). Thank you as well for your encouragement of traveling with our children. I have to say that while not expected, it is something we've heard (but never listened to) before. My brother-in-law used to always tell us, "Once you have kids, you're never going to go anywhere." How sad for us and our children if we would have adopted that approach to parenting.

Made a minor adjustment to the itinerary too. Exchanged out our stay in Samara at the Hideaway Hotel to stay instead at Villas Kalimba (which I 1st heard about on this forum) which will provide us with a kitchen so we can eat in when we so desire.

One last question, on our drive from Playa Samara back to San Jose, can anyone suggest a good place to stop to kind of break up our drive for the kids? Could be a good place to eat, could be a museum, something with animals? We're open to ideas.

Thanks again!