Things you've missed:
1. Assemble and test all your gear at home beforehand to make sure (a) it's all working (b) you haven't omitted an important part and (c) batteries, iPhones and laptops are all charged up. It never ceases to amaze me how many turn up at some remote location only to find they've left something behind or didn't charge a battery.
2. Something to warm/wake you up afterwards before driving home (coffee/tea) and a sugar hit (choc or a mars bar). Or a cuddly partner
Fires are not a good idea. In summer there may be a total fire ban, and even if not, if scopes are nearby the smoke is not good for optics plus the light pollution will be annoying. And the problem of making sure it's really out afterwards (esp in summer)... there's the question of both finding fuel for it and tidying up the mess afterwards. At the most a small gas ring and cylinder (the sort for camping) may be useful, but IMHO a thermos is a much better idea.
3. Make clear no alcohol otherwise the idiots will bring slabs and proceed to get plastered. A positive way to put this is to remind people they will be driving home late at night and driving and alcohol do not mix.
4. Depending how/where this is organised you might like to check your legal liabilities and consider insurance.