Big boy bed/baby in the crib

Question for the group as we're new to this big boy bed situation. We just moved our toddler who was already climbing out of the crib to his big boy bed (2.5) and our daughter (6 months) is now in his old crib in a separate room.

The problem is the child proof door handle things he can open and were worried he's going to 'share' his toys while were sleeping. And or climb in the crib with her and hurt her.

Anyone have suggestions for how to keep both safe?