Might be a little too aggressive.. not sure though.
I've had rainbows for a few years, but never kept them with anything small like puffers.
They'd be fine with your keyholes I think.. but the puffers I don't know.. might be something you'll have to try and see what happens.
Again though, don't get a pair... if you're going to get them, try to get 2 females.. when mine breed, they get quite nasty.. and pick on 5'' convicts.