As soon as OP is no longer flying the segment, those who have E+ seats are subject to losing them.

Those others will lose their seat assignment in E+ if any change ---- voluntary or involuntary ---- is made to the record. This could include an aircraft sub.

There is nothing to be done here to make the E+ seats stick, so just leave it alone. If the assignments survive, the others will be just fine. If they do not, they will be reassigned in E- and may select anything they want in E- or pay for E+ and hope to find the same or better.

Just leave it alone and keep your fingers crossed. Make sure the others know what may happen so they don't bother with a fuss if it does.

As to cancellation. Not to worry. Each passenger has his own ticket. That ticket is only cancelled if the passenger no shows (absent certain specialized tickets not applicable here).