you could just let him know you needed a date to be at the wedding, just to accompany you, nothing else but that, let him know you'll be very grateful that he'll attend it with you.
some guys just need reassuring and time to adapt to some ideas.
though you shouldn't have intro him so quickly to family members, ask him if things are ok.
you gonna show that you understand how he feels and more communication will be better.
gd luck
