Welcome to Flyertalk omk298, though I know this isn't your first posting. Welcome in particular to the BA board, and I very much hope that you can continue to be an active participant in this forum.

I presume you are referring to the Hold Your Flight Price facility. Now my understanding of that is that you have to confirm the entire ticket as booked, you are not able to make any changes to it at all if you wish to get a refund on the deposit. The one quirk, however, is that you can change the names of the participants, so you could replace the two travellers with two replacements - this is highly unusual on BA but is perfectly allowed here.

Otherwise your option is to confirm the ticket as booked, then cancel the non travellers, paying any fees or penalties, if that is more cost effective then rebooking 3 tickets at the higher amount.

You don't need to do anything about the reservation - it just lapses silently after 72 hours and the money is not recoverable.

I believe it's quite clearly laid out in the booking process, so while it is annoying from your perspective, it's your companions you need to discuss this with rather than BA! It's all or nothing. You can't even pay in a different currency after booking, which is normally ok to do.