Just wondering whether when you invite your DC's friends (in my Ds'c case he is only three so i am deciding who is coming lol!) do you feel obliged to invite the invitees siblings as well? In this case three of the little ones have siblings of just a year or 18 months old, DS knows them and as a group of mums we socialise regularly so it seem a bit mean not to invite them. The party we have booked is an activity party with food after, the little ones will not be allowed to join in with it due to 'elf and safety (gone mad!) but they would be fine to have the lunch after and join in with a few party games. If I don't include them in the numbers they wont get any food . Am worried the other mums will be annoyed that i am inviting the little ones to a party they will not be able to join in with fully but dont want to upset them by not inviting them- oh I know I am neurotic lol!!
well I haven't done a party like the one you describe... but for DS' 3rd birthday I assumed all siblings came as part of the package - afterall most were younger and so would cause a childcare problem. And mostly being 1 they don't eat that much and just need a basic party bag. One was older (6) but she is our neighbour's daughter and was really patient about being included with a load of 3 year olds - I think she would have been hurt to be left out. I guess it's more complicated with a party out of the home though, but if it's in school hours I think inviting non school age siblings only would be fine.
I'd do the invitation to the invitee and put a note with it/call the mum and say 'feel free to bring little x along too' and then you can discuss what they can join in with, what food there will be etc.