You definitely should talk with all before you sign up to share with to lay out what each will pay and any house chores, cooking, cleanup, groceries, car rental costs, shuttle to house, gas, etc. who gets up early, who stays up late watching loud TV.. Sharing is cost effective but has it's down sides unless you know in advance! Avoid the ugly!
As for rooms, splitting is easiest, and I think normally how it's done, although there can be grumbling about who gets the suites. I got stuck in a bug infested condo to appease one who had to have a king size bed suite. the place was a dump we passed up a much less $ super nice place (no king).. I ended up in an open loft that was hotter than hell with no windows, the bathroom was 2 flights down to a shared 3/4 bath, definitely not equal bedding arrangement but was a bed. I also didn't ask for $$ when a friend we invited to stay 1 night, only to have one that was part of the original split have a fit when she was out voted to charge the friend to sleep on couch 1 night or make other friends pay for the spare bedroom in our rental- my friends even brought their own linens, food and drinks! Another trip, one didn't want to chip in 20$ for groceries then took all the left over groceries home, she never even asked if the other locals, who did pay their share and got us an awesome price on the condo if they wanted to take food back home! I know a diva who got stuck with entire condo bill when friends changed their minds on going the last minute, and the condo was non refundable! I'm still owed $$ for a rental car one in our group decided she didn't want to pay for it because it sat at the resort (alta) it took months to get 4 days of her share in the 7day rental! I've watched some order up big $$ dinners then toss in 20$ that wouldn't even pay for their drinks, they leave, sticking others with their bill! Split checks are definitely advised unless you know who you are with and make prearrangements. When I get a ride with a friend I always give $$ for gas/insurance, wear and tear on their car, it's still lots less than me renting a car. I can't stand petty, greedy stingy crap, especially on vacation! It will all come out in the wash if everyone is like minded, with a sharing mindset. Sometimes it's easier to over pay to keep peace on trips and then not travel w/the offender again.
Trip insurance should be purchased and make sure you can get lodging $$ from insurance company, if you can't go, sometimes your room can be re-rented so no one is out $$ but life happens and you should think of this before it happens, you could lose all your $$ if you can't go. Flight delays have caused me to miss nights- I still paid for those nights as I should have.
Menu planning on fly in trips is best way to go- know what everyone likes, allergies, gluten free, veggie etc. speciality items, alcohol. You do not want a ton of left overs, although I'm sure the housekeeping staff has enjoyed some of our goodies we've had to leave behind. We've always just split it up with how ever many were in the condo no penny pinching when splitting cents.
I'm now finding organized group trips w/set prices and having your own group within the bigger group to make up "your" condo are very economical and lots of fun. This year I have a few group trips out west, one is less than 2K includes RT Airfare from albany, the RT bus ride from montrose to slope side lodging at Telluride for 7 nights, a welcome party, goodie bag and more! There are no surprises or extra costs just food while there. I'm already signed up for a few trips next year, they are so simple, just get to the the airport and everything but groceries is done! Another diva has invited me to stay w/her out west, to me it's the deal of the century so yes, I will be buying her dinner (s) as appreciation for the savings she's sharing. Like wise a couple other trips- just like when I'm a guest in someone's home i bring a housewarming present, or buy them dinner out, definitely always share in the food costs. It can all be so easy!
I'm happy that I have had WAY more good trips than bad, I have met life long skiing travelling friends that I can plan ski trips with, we can just send a check; for 'how much we owe' to who ever puts it on their CC and know it all comes out in the wash.