POD to what JenJay said.
I, too, am raising an eyebrow over the bachelor/bachelorette party thing. And just how many weddings/receptions does a person need to celebrate being married? Once the I Do's are said, you don't get much more "married" than that. They already had their "big day" when the JP did them the honors.
The only time I'd consider an exception is if a couple wanted to renew their vows for a milestone anniversary (say 25th or 50th.) Then a small token gift or a card expressing your best wishes would be appropriate if you so wish. In this case, though, I'm having a hard time not viewing this couple as attention hounds at best and serious gimme pigs at worst.
I say skip the gift. I'd skip the wedding, too, but that's just me.