AA does allow carseats (not infant carseats, though) to be used on board, provided it is in a window seat in a non-exit row (per FAA regs). I don't see why you can't bring the stroller through security. I've taken our double jogger through at ORD, HNL, and ATL. I assume it folds up, as you will have to gate check it - can't bring the stroller into the cabin.