Who To Invite?!

Ask them they would be able to give you a list of people they`d like to be there. You could also ask both sets of parents for lists.
Tami

Yes i agree ask them. I personally think that friends and family should be invited to an engagement party, remember these are the people that your sister is going to most likely want at her wedding so it would only be fair to invite them to this, if i was not good enough to be invited to an engagement party there is no way i would except a wedding invite either, thats my opion but.