In your situation, I would be looking at this
Outlaw Audio subwoofer. It has down-firing driver and ports, so those are not exposed to children. It's a bit expensive, but it is a very good performer. If your kids do climb on it, it can support their weight without problem.
As for speakers, it looks like tower speakers are out. They will be a safety hazard with your kids, and your kids would probably destroy the cones anyway. In-wall speakers will have to do.