We also had this problem... But we were not friendly with the neighbors, so... We didn't care about tact unfortuatley. We just took their child by the hand and deposited him back on their porch and rang the door bell. It is VERY bad parenting to just let your kids roam and go to a neighbors .
Now we have other neighbors who if our kids want to go over each others houses we always look outside and call down to see if it is OK to let our child come down and play and feel very comfortable saying no if the time isn't good.
In our old neighborhood, a family put up a flag pole. If the flag was up, your kids where welcome to come and play, if it was down that it wasn't which worked out great.
It's very unfortunate that there are parents out there that put us in this perdicament(sp?). I thought we as parents are suppose to watch our own children??? And being a parent we all know how hard it is sometimes to wath our own children, get things done around the house without having to watch all the neighborhood kids.
In regards to snacks... I tell my neighbor's what my kids can and can't have. I think it's a pretty open conversation these days with all of the allergies. Little girl neighbor allergic to nuts, little boy neighbor allergic to milk. So I just had both parents make me up a list of what they "can" have and I keep it taped inside my cupboard for when they come over, if I have it they can have it. If I don't then they need to bring their own snack.
Sorry for the book!
J. in Macomb