So what has the OP learnt from this?
Various options:
1. Call the airline at the time of the booking and explain to make-up of the party
If the airline can't/doesn't want to block 3+2 adjacent seats
2.Check in online 23 hours before depart
If there are no 3+2 combinations available,
3. Talk to the check-in supervisor and sort it BEFORE getting onto the aircraft