My suggestion is to host at one of your houses if possible, or if it is not possible for one parent to host each week, then why don't you make a list and each parent can sign up to do a few weeks during the school year on a rotating basis. That way, the scenery changes, and each week there will be new toys for the kids to play with, along with the teacher's ideas for the class. You can all volunteer to pay the teacher each month what you would have paid her if she still worked at the school. This way, you get the pre-k teacher you want, the same kids will be together, and as the parents, you can help make this year special for your children. Though this scenario will be more work for the parents(the hosting parent each week would be responsible for providing the snacks as well as their house), it will be valuable for your kids seeing you work together so they can stay together. My playgroup did a similar thing, and some of us(including me) are former elementary school teachers who are now SAHMs. I hope this idea works out for your group so that you can stay together.
H.