Hmmm - I know you said that you and DP can't lift DD to transfer - would she walk without much issue from her bed to yours and still go back to sleep? Thinking you might have to go a few nights of leaving the room when he gets silly (is this something that would work for him?) and then returning when he is lying down/calm/quiet? Might be initially a longer process but should become much quicker with time? Don't know if that's an option that would work/you are comfortable with?

Other thoughts - I know my sister used to lie on the floor/doorway until her DS fell asleep - would leave if he wasn't lying down/being silly etc. Initially it took over an hour plus and then reduced. Don't know if that could work either?