Some people are just socially dense when it comes to knowing what to do. I know because I can be that way. I can be just utterly clueless. Whenever there is a group of people involved its easier for us clueless ones to think that we aren't needed or that the situation is under control.

The best thing you could do is force the issue. Don't wait for them to offer help, say "I need YOU to come and help - show up on this day at this time".

Who knows, it just might work.