Colombia with a 20 months kid

Hi everybody,
My wife and I are planning vacations for this holiday season and we consider Colombia as a possible destination.
We are used to backpacking and local transportation but now with a 20 months baby it's time to adapt :).
So we were wondering if spending 10 days in Colombia in 2 or 3 different places could be an option. With just a high level of reading of the country we were thinking of spending time in Cartagena and in Tayrona. Ideally we'd love to be able to do daily hikes (with the kid in a backpack on our back) and diving if possible. We know we'll be limited in our move so we need to stay longer in the places we'll pick up. Are these good choices? What do you guys think?
Are there any better options?

Thanks for sharing your experience!
Cheers,

Patrice, Sophie and baby Thomas