G.B.
You know, if I was doing wedding invitations I would never think to add each individual person in the family. I think that's a lot to expect anyone to do.
I'd call and ask a family member. When I was addressing invitations to my wedding I never thought of anything more than whether to put Mr. and Mrs. XXX or by Ms.XXX or other.
Call sister/brother and ask them. Tell them you're planning on spending a few days and you need to make plans as to whether the kids are invited or not. Then ask them if they can offer any suggestions as to a good babysitter.