Upvote:1
You have a bunch of options:
Just book it now and pay a change fee of you have to rebook. You'd have to pay the change fee plus any fare difference between new and original flight. Some airlines will let you keep the original price minus the change fee as credit for future bookings.
Most airlines offer "flex" tickets, which waive any change fee if you rebook a flight. The cost adder for those is all over the place: I've seen it for as little 10% to triple or quadruple the price for a non-flex ticket. You need to check your specific itineraries. Buying a flex ticket with an incremental cost of more than the change fee, doesn't make sense. Even if the change is waived you are still responsible for any fare differences between the new flight and the original one. That goes both ways, though: if your new flight is cheaper you actually get money back.
Just wait it out: Typically flight prices don't go up that much unless your are travelling during peak season or a major holiday. You could all book now and then when the last member of your group is ready to pull the trigger, book a matching itinerary then. It's unlikely that prices will rise more than the change fees. You can also keep monitoring prices and make the call once you see seat availability going down or prices going up.