Hmmm, I don’t personally have any experience bunny boarding. But thought I would pop in with a few thoughts.
I think its a positive sign that you popped in when you weren’t expected and say things up to good standards. I would personally pop in again on a different day to see again how things are run and done and to double-check.
I wouldn’t be too concerned about the size of the run since this won’t be a long-term thing. As long as they have some room to run a bit and binky around I wouldn’t worry in that regard. We had a condo explosion and were displaced with our five buns one time. We had to go two weeks with four of mine in ONE x-pen, haha! They weren’t too thrilled but they were still happy and binkied and they lived through the horrible human reducing space for a small amount of time.
As for the reactions to other animals – I would ask if the lady would be willing to maybe put up a towel around a corner over the top of the hutch. So if they get stressed by the other animals, they can go in the that specific corner. Or even if you brought a long a cardboard box that would fit in the hutch that your buns could “escape” into if they didn’t feel comfortable.
Not sure how helpful this is (I’m sure others will be along with more advice) but thought I would give you some thoughts I thought about when reading through your post.