Hi, Despite what others say, in most parts of the country a pool is usually a negative selling point. More people will shy away from a pool than be attracted to it when shopping for a house. Some of the comments in the other messages sort of prove my point. If you are scared by it with a young one, and you could use the extra lawn space, just do it right and have it filled in. Any scheme that would "cap" it is not practical and would cost a lot of money, leave you with a dank underground space, and not give you the lawn you crave. Fill it in, but do it right.
Your town or city probably has a "pool demolition" code. You probably need to follow it and get a pool demolition permit. Even if your town doesn't have one, you should probably follow a similar procedure. 1. cut holes for drainage, 2. Fill bottom with gravel and/or sand and compact each layer. 3. break up the top part of the pool and carefully mix it in with clean fill to fill the majority of what's left, taking care to compact often and not leave any voids. 4. Top dress with loam/top soil and have fun on your nice, safe lawn. I am no expert, I just did a "power search" on metacrawler.com using pool demolition as a phrase and here are some of the results: