Invitee age group: - kids need less food than adults

- adults don't need nerf guns

- kids and adults have different drink preferences.

Ability to group invitees into families:

- whichever parent is 'in charge' of plans for that weekend can respond

- whichever parent realises there's a change of plans can edit one or more of the RSVPs

- often a family will accept/decline differently for different members, e.g. older sibling isn't interested, or one parent will run errands whilst the other is at the party