while I appreciate other peoples food values if someone said to me "Sorry we don't do Maccas parties" I would be pretty miffed. Partly because I would feel like there was an element of snobbery and partly I would feel bad for my child and for the OP child as they would miss out on seeing their friend.

I would rather someone just RSVP's "NO" with no explanation but then thats me.
OK now I’m getting confused (I knew I would) because I’m getting conflicting opinions. Some say, please do explain, other say, I don’t want to know the details.

hmmm... i think i would be a little offended! sorry! only because if i were to have a maccas party for my child it would be because i thought my child would really enjoy it and i would then think.. well whats wrong with it? IYKWIM??
I guess this is the thing for me. Anyone having a McDonalds (or similar) party should be prepared for people to decline because there are people in our society (ME) that have strong, real and completely valid objections to them. JMHO.

Thanks again for all your feedback.