We moved when our kids were about the same ages as yours. It was in the 3 weeks that fall between their birthdays. Son was about to turn 7, daughter had JUST turned 4. Had always and only lived in the one house, and they both had their own rooms their whole lives and had been fine.
When we moved, we were building our new home, and had to live in a rental during construction of the house. For about 10 months, we were in a 1,000 sq ft townhouse. 2 bedrooms only. So they shared a room. It was tight, so we didn't even put up their bed frames--just put their mattresses/box springs on the floor, to save floor space. Daughter had a twin, son had a double. They really liked sharing a room, and I hated that they got more and more difficult about going to sleep once they went to bed. :(
But, at the end of the rental period, when we moved into our new house (where we still are now) they went directly into their own rooms across the hall from each other, and at the complete opposite end of the house from me and husband (pretty much like in our first house, lol). They were excited to have their own space again, but since our daughter was afraid of lightening storms, and has a huge double window in her room, we let her camp out in his room if she was afraid during bad weather.
They are 11 & 14 now. And up until about 2 years ago, they would still periodically ask for a "sleep over night". They are really close to each other, and so we allowed it sometimes on weekends, with one on the floor. They don't ask anymore.
I wouldn't turn either of your kids' rooms into a playroom. I would expect that they will get past this phase, once the newness of the house wears off some more. Give it 6 months, and re-evaluate. I do like the idea someone suggested of putting bunk beds in one room, so the kids can decide to change rooms during the night if they "need" to, but still have their own space as they want it. If you combine all their stuff into one room, you will have some arguments/bickering over space and such. Trust me. You don't have it now, b/c it is still your daughter's space/room. They only are sharing when they are both asleep. That is very different than daytime sharing.