I found Iguana Lodge on tripadvisor as one of the top family lodgings in Costa Rica and I'm glad to report that we're back from what was by far the most amazing family vacation we've had. My boys just turned 3 and 1 and it was a perfect place to experience all the wildlife of the Costa Rican rainforest without having to leave the resort! Obviously we couldn't do lots of tours with the little kids, but we got to see white-face Capucin monkeys, squirrel monkeys and howler monkeys almost every day at the resort, one day they even hung out above the Rancho while we were having breakfast! We saw toucans, macaws and iguanas right from our huge private porch!
Even before we arrived, I was amazed by the customer service provided by Maxine, their reservation person, who basically became my Costa Rica travel agent after the others that I talked to didn't provide the service I had hoped for. She helped us book all our intra-Costa Rica flights and even got Sansa to run a flight for us (not a charter, so regular prices!) on our arrival date so that we wouldn't have an overnight stay in San Jose. She worked with the team to organize a crib and child seat for the table for my one year old, and generally answered all my many many questions very quickly. I had been told by another agent that the Osa was too remote and not a place for little kids, but I'm so glad that Maxine convinced me otherwise.
The staff at the lodge and the restaurant was also amazingly friendly and accommodating, they carried our baby around all the time so that we could eat, attended to every need immediately and were more warm and friendly than at any other hotel we've visited.
I can also echo all the other great things mentioned in other reviews; the food was amazing, and we're very picky and my husband is not a fan of eating pre-selected meals, but he absolutely loved it too. When the dinner selections were too spicy, we were able to get kids meals from the Pearl restaurant at no extra charge. I could go on and on, but let me close with the amazing BBQ dinner we had on the beach on Dec 25 - the food and tables were set right on the sand and a huge bonfire and fire-powered paper balloons made this one of the best Christmases of my life - and the best part is, they do this every week not just on Christmas day!