I bought some of those IKEA 'air elements'. Basically, they're just big air bags made of thick plastic with covers on them. We have a lady bug, elephant, turtle and some brown animal (groundhog maybe?). They're akin to bean bag chairs, but with air in them instead of beans or styrofoam and are super durable. I've had 2 of mine for about 6 yrs with only one air element biting the dust. They're great as the kids can bounce on their bums on them. I've found them pretty good for burning energy in the winter months. I can't remember the prices off the top of my head, but around $40 each for air element and cover together maybe. Plus, they stack nicely in the corner and can be used as chairs at reading time, etc. Thick foam pads or old couch cushions are great too. I would get kids to take a couple running steps and jump onto them, one at a time. This time of year is soooo tough for keeping kids active! They have to burn off a little steam or they'll drive you out of your mind!