Time for your son to keep these kinds of things in his room and if he wants to go in there and close the door and play with them that is ok. It is his house. He is not obligated to come and entertain the daycare kids.

If older daycare kid puts up a snit well just tell him why he lost the privilege. He can not be trusted to play properly and to put things back when he is done with them.

Another option is to keep things like this under your control so if they want to play they each choose a figure and one accessory from your collection and must return both items when done - before leaving the house but I would be watching them and as soon as interest wanes collect the figures then.

I had issues with the girls and barbie doll shoes and clothes and that is what I had to do. They were allowed to choose one doll each and five items of clothing. All accessories were for my own girls after hours so dolls walked around shoeless and purseless at daycare.