I would offer them 31 and 45
Don't think it gets done for that, they want to get into the 1st.
I'm pretty sure there was info out there that #22 + contract has already been offered, so that's your baseline.
I'd point out that the choice of contracts offered are for unwanted players with multiple years left. It's not a great offer. 31+45, with no salary going back, is very arguably better.
That said, Thad Young is not a player who will take the Celtics to the next level, nor do I think he's a player the Celtics can trade for someone who will get them to the next level, so I'm not interested.