First, congrats on the nice present. Second, my condolences. I hate to sound like the voice of doom here but, you did mention that 2 of the guests are "seasoned outdoor cooks". This tells me two things.
1. They'll pounce on each and every little perceived imperfection in your recipes and technique
And 2. No matter what you cook or how masterfully you prepare it, they will have been able to have done it better. Just ask them.
My best suggestion would be to go as simple as possible with something that's as close to universally liked as possible. Chicken and ribs, as simple and safe as they seem, are absolutely fraught with peril. Just look at the contentious posts on this, the friendliest forum on the 'net, regarding these 2 meats. Chicken has skin, which you likely won't be able to get "crispy" and if you do it'll likely look like a meteorite. Then there's the knife edge point where it's "done" but not dried out. It's either going to have some pink around the bone or the white meat is going to be dry. And yes, I know a seasoned outdoor cook shouldn't be scared off by a tiny bit of pink, but it's ammunition to show how your chicken is inferior to theirs. I had a relative at a dinner party once point out none too quietly that the meat around the breastbone of one of the pheasants I had shot, cleaned and grilled was ever so slightly pink. Have you ever tried to grill pheasant and not dry it out? It's a serious pain. This was as close to perfection as any grilled pheasant has ever come, and it still wasn't good enough.
Then there are ribs. Just get that crazy idea out of your silly little head right this instant. Seriously, there are few things on Earth as hotly contested as BBQ'd ribs. There are just too many variables, from the cut, to the texture, to the sauce vs dry debate, to the rub and on and on and on. And since it's all a matter of personal opinion, your ribs will be wrong no matter what.
No, what we need here is something that isn't subjective, that will set your guests salivary glands on high, and that given the new machinery, won't be terribly taxing on the cook. I'm thinking BEEF!! Namely something fancy enough to wow them without seeming pretentious. Tenderloin is too fancy and sirloin is too pedestrian. The rib roast, however, never misses. ( or tri tip if you can find it)
You can do a reverse sear to a perfect medium rare-medium and do it all to specific temperature, thereby removing all guess work. And, should one of your know it all guests complain it's not done enough you can very smugly remark that your beef is PROPERLY prepared, but you'll be happy to toss it back on the grill and ruin it for them if they so desire.
Look up Bearcarver's step by step tutorial on rib roast and Cmayna's recent post on reverse seared tri tip. Those both should help you wow your guests without giving yourself an ulcer in the process. I wish you luck and don't forget to let us know how it all turns out.
