
Glad to hear things are going better. You might want to try a baby gate as long as no one will jump it in the house to practice, that way you can kinda watch all your dogs at once and still focus on and do obedience with Bumpy. I use a baby gate often for dividing up space to practice inside. Mostly obedience type exercises, our agility stuff is outside.
A crate sounds like a good idea too so no more destroying things while you work with Bumpy. Maybe give a super tough bone, filled and frozen Kong, or buster cube before you go outside to work with Bumpy, that might keep them busy too and give them somewhere to direct attention, you will want to put them in their separate places of course where they can't get to each other or see each other since you are not there to supervise the interaction. But then again, you really want to be around when they are chewing a bone of any sort even super tough nylabones, so that is not an ideal best situation. Kongs should be okay, but I think you need to be around to watch that too, as I have had a Kong get stuck on my male's muzzle before. Better yet your significant other can keep an eye on the dogs inside, while your practice with Bumpy.