DS's party next week (talk about leaving things to the last minute!) is somewhere where there is a strict limit on the amount of children allowed. In the past I've always had a few parents bring along the siblings of the invited child, which is irritating enough when you're just doing the party yourself and haven't catered for uninvited siblings. But in this case they won't actually be allowed in so I want to mention this on the invites. It's not rude if I say something like "sorry that we can't invite brothers and sisters as well, but the venue won't allow extra children", is it?