My guess is he will he would NEVER rest all three of them in one game.
My second guess is if this roster is intact after the the trade deadline, that means Doc has the go ahead to do what he can to win the division and get the best chance to maximize profits by getting an easier first round opponent and more homes games with a potential second round appearance. I have read that each home game in the playoffs generates about $1 million of revenue for the Celtics. No small amount of money.
If Doc has the go ahead to win win win, then that could mean he wins at all costs. The only rest any of the Big Three will get is if they are able to blow out the Kings, warriors, Hawks and/or Bucks and get to sit in the fourth quarters and play less than 30 MPG.
If Danny blows it up and keeps a Big 4 member or two, my guess is they suddenly end up with a season ending injury and will be getting tons and tons of rest.