Group Shelter Recommendations

Check out rei. They've got those monster group ones that you can buy garages/connecting tubes for and literally make a multi tent mansion.

Otherwise, Big Agnes will probably be your best option (unless you make a tarp shelter to hang out in). Specifically, their Wyoming trail line.

It's a tent with a giant vestibule, they even make a 4 person, with two separate sleeping quarters connected by a huge vestibule that can open up and have trekking poles used to make an awning with the door.

https://www.bigagnes.com/Products/Detail/Tent/wyomingtrail2camp

The SL version is a couple pounds lighter, but $150 more expensive and the vestibule door can't be extended to create an awning.

Big Agnes has outstanding customer service and lifetime warranty, so you'll never have to worry.

Course, at about 7# and 9# (15# for 4 person version), not exactly lightweight, but if you're car camping, it won't matter. Also, if you're group camping, just split the weight up with everyone. Even the 2 person one can sleep 4 if a couple people sleep inside the vestibule (as if sleeping under a tarp) then the weight could be split up 4 ways, or two people can carry the shelter, the other two carry all the food, etc. The 4 person one could sleep 6.

How many people?

When there are 4 of us a 10×10 or 10×12 is plenty. We all use adjustable trekking poles so we have plenty to work with. Stake the "back edge", place a set of poles to form the back wall, move out 6' and add another set of poles to hold up the porch. Lower one corner of the porch a little so water runs off and doesn't pool.

Because you have good control over where you pitch, you can ofter include a sitting log that happens to be facing a fire pit, if that is a priority. We usually go for view, break out the stoves for soup and drinks, and enjoy the day.

Actual setup takes less than 10 minutes. By Day 3 everyone knows what to do and it's done in under 5 minutes.

YMMV

+1 on simple tarp, easy as pie and you can still set by the fire. 10×12 is perfect for 4.
Mind you Silnylon will simply disappear if flames hit it.

What about two Space All-Weather Blankets (the more substantial ones, not the thin mylar ones), set up as opposing 2-person lean-to's, with the fire in the middle? This allows you to keep individual shelters, better than a large 4-person shelter that requires a large set-up area and still allows everyone to bring what they want (UL tarps, traditional tents, etc).

Each space blanket is only $17.00 at REI (maybe cheaper elsewhere), light enough at 12 oz, durable enough but no big deal if something happens to it, multi-use (extra groundsheets, emergency warmth, etc) and would need only 8 additional stakes (4 each), maybe two 6' foot pieces of guyline and some sticks or trekking poles to get a basic temporary lean-to.

These: http://www.rei.com/product/407106/space-all-weather-blanket

Edit: not sure if I was clear; I mean making a sitting-area with these, but still taking separate sleeping shelters.

A related question–hopefully not derailing the OP's. I started taking a Noah's Tarp for small group camping with rain forecast, after I got completely rained out one morning with no group shelter. My plan is during rain to pitch it angled with the highest corner just barely over the fire. I just want to stop the rain from extinguishing the fire, and have a side we can sit on. This is for where fires are permitted and typically there is even an iron fire ring. How far above a "typical" camp fire will I need to put the tarp when I eventually have to use it? Weenie-and-marshmallow-roast sized fire, not a few small sticks but no more than two logs, flames usually no more than a foot above the ground. Thoughts?

I don't mind the occasional ember burn hole, which is inevitable, but I'd like the tarp to last more than say ten uses.

Forgot to KISS with my earlier suggestion. You could always go Walmart blue tarp and see how that works for the 4 of you before committing any more $$ to a more expensive shelter.