Two questions come up more than any others before departure, and both have short answers.
Money
Cards are accepted in hotels, in the large shops and in most restaurants. Carry some riyals for the smaller shops, the barbers and the taxis. Exchange rates at the airport are worse than in the city, so change a little on arrival and the rest later.
Phones
A local SIM is cheap and is sold at the airport and in every mall. Hotel wifi is usually adequate for messages and unreliable for calls.
Roaming
Check what your operator charges before you fly. It is occasionally reasonable and it is occasionally startling.
Keeping the group together
One group chat, agreed before departure, with everybody in it. It is the single most useful thing a group can arrange.
