H.M.
We are in the same situation. 2 year old boy and 4 month old little girl. We bought a toddler air mattress (has a "bumper" all around the bed.) We placed it on the floor next to his crib. He loves it and is adjusting to a new bed in the same room. We can lay on the air mattress with him and read at night. It was about $65 including the sheet on amazon.com & is a great transitional piece. Next we will move the bed into a new room so his sister can have the crib in his old room. So far it's worked like a charm!