Here is what I suggest:

First, flip a coin to see who gets in the seat first.

When you are all seated on the plane, you and #1 upgraded, and #2 in coach, have a quiet word with a flight attendant. Explain your situation.

If the FA agrees, then midway through the flight, #1 and #2 switch. Do it quietly and discreetly. Agree on a midpoint time, so all are prepared. Make sure that both #1 and #2 know which seat to take when they make the switch.

#2 in Coach might want to alert their seatmate, so the seatmate doesn't wonder why one got up and another came back and sat down.

Finally, consider carefully how #1 and #2 will handle all carry on luggage. Make sure each knows exactly what to pick up and carry out of the plane. You wouldn't want #1 to leave #2's laptop bag behind just because he didn't know to pick it up and take it.