T.O.
C.,
Personally, I would think you're crazy if you put "no firearms" on the evite. However, I would expect concerned parents to ask me and I would be prepared to answer those questions. Concerned parents call ahead of time. The rest don't and won't care.
I "questioned" every household I let my children stay at without me when they were younger. The gun question was always on my list.
Food... you shouldn't worry. Just have a variety. If someone has an allergy the parent will tell you when they rsvp then you can adjust.
And I never went to a party at that age that the parents weren't welcome to stay at too.
Sleep-overs... it's a little young, but boys usually grow out of it soon and girls NEVER do.
Have fun.