Hi, I´ve used a few times www.explornatura.com, I did the canyoning and zip lining with them, and I love it! They have their main offices in Turrialba, however they also have offices in Arenal area. Prices on their tours are reasonable.
hope this helps.

For your time in Arenal, I would go into the town of La Fortuna and just walk around a bit. There are numerous tour operators and they post discounts every day. This would be your best bet for getting an economical tour.

Here are some suggestion based on what our family enjoyed (no particular order)

Arenal: Sky Trek for zip lining, eco thermales for hot springs and dinner (food's surprising good), hanging bridges (pay to hire a guide) and also the cafe at the entrance is quite good. La Fortuna waterfall (we took the horseback tour and had a great time. However, the horse tour only allows for 75 minutes or so at the fall).

Manuel Antonio (we stayed Buena Vista as well...great spot): Be sure to eat & get coffee at Cafe Milagro (there's one within walking distance of BV), white water rafting (fun but certainly not as wild as the rivers to the north. We used Rio Tropicales (sp?) and definitely recommend them. FYI- the beach at BV is better than the national park (IMHO)

Enjoy!

I'm having a hard time finding a white water rafting trip for us, as my 6 year old seems to be a bit young. Anyone know of any company that can accommodate our 6 year old?

just came back (two days ago)If for any reason you need to use a shuttle, STAY AWAY FROM INTERBUS, used Grayline or other companies.

Madana, this people that I recommend before, Explornatura, they have special rafting for kids, however I am not sure what is the age limit. You could check with them.

Prisca, we've heard you loud and clear. You didn't like Interbus and I'm sorry, but your one experience will most likely not sway the rest of us from using the company. Yours is the only bad review I've ever heard. Do you have anything GOOD to say about your trip? Anything positive to talk about?

As for Madana, I would do both the zip-line and the ATV tour in La Fortuna. This area is great for all adventure activities. I don't know about the rafting so can't help you there.

Manuel Antonio is great for hiking the park, horseback ride to waterfalls, sunset cruise and lazing at the beach.

You will enjoy both areas, I'm sure.

I'm pretty sure the youngest they allow for rafting is 8. My son was 9 and we went on the Balsa near Arenal. We used Fourtrax for the ATV in Arenal. In Manual Antonio we booked most of our tours with Iguana tours. I highly recommend the Dames Island Mangrove tour. The timing of this tour is based on the tide. I'd check with them as soon as you arrive in Manual Antonio. They also offer a Manual Antonio park tour - we had the best guide - Mauricio!