Hi P.,
we are in the same boat! (except I am due in the end of May, so we have been working on this for a long time!).
and - I only have one daughter, and the other bdrm was our office. We decided to get rid of the guest room, since we only use that once in a while, but we are in the office every day! I took the double bed from the guest room and made it into my daughter's "big Girl" bed. We painted her new room pink (just as she requested), and made it pretty.
I took the bed off of the wheels, but did keep the mattress and box spring. I had a little step stool for my daughter (which was being stored in a closet!) - now she uses it to help her climb up onto her new bed. I have one side up against a wall, and have a guard rail up for the other side.
The transition went very well!
We had been reading books about new babies, and one day my daughter asked "Where is the baby going to sleep?", and I asked her if she wanted a big girl room with a big girl bed, and she was thrilled! She loves her room and her big girl bed (but I do have a gate up over the entrance to her room) so that when she wakes up early, she isn't roaming all over the house.
This weekend, we are having company, and my daughter will give up her bed to grammie and poppy and we have borrowed a small air mattress for my daughter - I hope it goes well!
(DD will share the room with grammie and poppy).
Wish us luck!
Good Luck to you, and remember, someone once told me - the little ones are more flexible and able to tolerate change, it is us grownups who get used to things being a certain way and have a harder time with change!
Warmly,
E.