Welcome to FT!

As nako stated, most FFPs only award the miles to the passenger whose flies (BIS - Butt In Seat). If you purchase the ticket(s) with a milage earning credit card, you would get the "miles" for the cost of the ticket(s) - but not for flying.

Yes, you would earn miles for flying yourself also, but not also for the other six. They will (if they join the FFP) earn their own miles. If they do not join the FFP, the miles are lost and nobody earns them!

Each person flying should (but it's up to them) join the FFP for themselves, and then maybe when they earn enough miles, maybe they will give you a free ticket! (When my sisters have flown, I signed them up for the FFP. Who knows, I may be given a free ticket someday as a present! )