Kids need to play with dirt to build a strong immune system, yes.
As I'm not an expert on what diseases/parasites/viruses a squirrel might carry I can't side with either of you. I wouldn't be surprised if a child was more at risk of parasites if they played in a sandpit than if they picked up a dead squirrel, mainly because kids will play in a sandpit a lot more often than they'd pick up a dead squirrel. Tell the kids to wash their hands and take the squirrel away if you're so paranoid.
Kids need to play with dirt to build a strong immune system, yes.
As I'm not an expert on what diseases/parasites/viruses a squirrel might carry I can't side with either of you. I wouldn't be surprised if a child was more at risk of parasites if they played in a sandpit than if they picked up a dead squirrel, mainly because kids will play in a sandpit a lot more often than they'd pick up a dead squirrel. Tell the kids to wash their hands and take the squirrel away if you're so paranoid.