I think I have over complicated things...
DD2 will be 8 in Dec, DD1 will be 6 in September.
So we decided to throw a joint party at Halloween (roughly in the middle of both their birthdays). They will invite about 20 children between them, some know just DD1, some know just DD2 and some know them both.
How do I word the invites? Do I do three separate types of invite? (1 saying dd1s party, 1 saying DD2 party and 1 saying DD1&DD2s party?) I mention that it's technically a birthday party even though it's not actually close to either of their actual birthdays?