Hi Dixie. I second the idea of sugar-free homemade ice cream! I bought an ice cream maker after our wedding so I could do just that. I haven't made it as often as I want to because it doesn't store well and it's just the two of us, but with a big group, I'm sure it would be polished off.
On the subject of whether or not you can go back and indulge... it depends, and hopefully you'll figure out your sensitivities. For me? I had about 8 "freebie" years as a LCer with those occasional treats that didn't seem to do any harm. But then age happens. Arthritis and gut problems happen. And then they get worse. So I had to fine-tune and experiment. For me? In addition to staying low(ish) carb, no gluten, ever
. I didn't want to believe it and was in denial for a while, but eventually, I realized that the drawn-out suffering wasn't worth a few minutes of scarfing down crap food, especially when most of the culprits were easily replaced.
Something I'd recommend to anyone is a good elimination diet at some point - not necessarily while you're still a newbie and trying to find your footing. Eat a strict paleo diet for a while with very "low reaction" foods, and test one thing at a time, in particular if you notice flare-ups in certain conditions and you can't think of anything else that would cause it.
If you're looking for tips at all on "big family meals on a budget", feel free to start a thread and describe what your cooking conditions will be like, as well as what general area you'll be in (this is an international forum.)
There are lots of LC-friendly meal ideas for feeding a crowd, but costs vary by location.
Best of luck!