I am having a significant birthday party in 4 weeks and have invited friends and family by fb invite, phone or in person. The hall holds 100 and I have invited 100 but almost have have either not replied or have said they will 'try' to come. Is this usual? Should I over invite to ensure some people come?Are non posted invites ignored? Also need to know about numbers for food. Grrr...rembering why I never throw parties!