How to word Jack and Jill shower on invitation?

So, as some of you may know I'm the MOH for my friend's upcoming wedding. Her shower is going to be next month. They want to do a casual cookout, but this, "shower" will be huge and co-ed, b/c she wants to just have one big one, with both sides of the family AND friends.

Is there a good way to word the shower invitation to get this across? I get the feeling there will be many more relatives there than friends, so the crowd will be older, and maybe not used to the idea of a jack and jill shower (FWIW, I had one 10 yrs ago for my wedding shower, BUT it was just friends). It's going to be a cookout at her parents' house, and there will be a ton of ppl there. The only, "game" we will be playing (I'm going to do a cooking activity with the bride and groom, and idea I stole from another friend who went to a bridal shower recently), they are not into games, and are both past 30, and just not into cheeky stuff, kwim? So, it's like a party, with shower gifts, the one, "game" for the bride and groom, but the groom doesn't want to call it a shower, b/c he says he feels weird going to a, "shower," b/c to him it's a girl thing...

DH and I had something similar for both our wedding and when we were expecting DD. The invites were worded for in line with a party and they talked about "celebrating this time with the happy couple" or something to that effect. And we didn't play any cheeky games...I cringe at the thought...but everyone got that it was a more modern spin on the traditional shower. GL!

I agree with PP, just say "come join us for a BBQ celebrating Jack and Jill." I really don't see the need for much explaining. I think you should give the old folks more credit. ;-)