According to your post, you can legally fly this aeroplane already. If that's right then you don't need to be "signed off" by the PPL as current on type.
So, since this isn't a legal matter, it's just a good sense matter. You can decide that as well as anyone else. If both you and the PPL holder are legal to fly the plane then either (but not both) of you could be P1 for your flight. If you are P1 and you are legal to instruct in the type then the PPL could log PUT also. Neither of you could log P1s since this wouldn't be a flight test.
From a common sense point of view, the PPL holder who sits with you must be fully competant to recover from anything you might do while you are regaining your familiarity. I shouldn't imagine that most PPL holders would know when to take over controls during landing as an instructor would - so you'd have to be pretty careful here.
You also need to check the group rules and the insurance words to make sure that you are not about to invalidate that by having the wrong one of you as P1.