In response to a few replies, I really don't know whose idea it was for these kids to come up here. I don't know if my son just wants to spend time with them (my kids are all pretty close to their cousins), if he specifically wanted them to have fun on my new property (which has some really neat things on it), if they asked, or what. One of his aunts lives about 45 minutes from me so I don't know if they all planned on visiting her, too, and he didn't want to drive out there to drop them off first and then all the way back to see me.
I have told my son it's not a good idea and if he wants to bring them to visit their aunt, that aunt and their mother will no doubt reimburse him for the extra gas to bring them up for a visit.