G.B.
To be honest I would put them in separate rooms. The baby isn't going to be able to play in the play room due to the toys not being age appropriate.
You will be constantly having to sit in the room and grab toys out of the babies mouth. Or the older child won't be able to have hot wheels cars, legos, blocks, any toy that will fit through a toilet paper roll, clear until the baby is over 3 years old and NOT putting anything in his mouth. My 4 yr. old still has some toys he can't play with due to them going straight to his mouth.
The bay will want to crawl and play with toys that appeal to him. He needs a space that is totally baby proof. That seriously limits the toys the older boy can even have in his room. That just doesn't seem right to me. So that's why I say keep their rooms separate.