My son used wood in the cage this past off season. This was the first time he has used it. He really learned where the sweet spot is. About two weeks before the season started he switched back to his 1.15 . There is a Huge difference, as you guys know. MY question is should you stop practicing with wood when your season starts? Would it mess up his swing if he uses both (he also has a bbcor bat)?
No, in terms of hitting mechanics, using wood bats would not "mess up his swing." But using a wood bat as much as possible does get a batter to learn how to square up (particularly with various pitch locations) and as you mentioned, "where the sweet spot is." The "better" college summer leagues all use wood, so maybe that might say something other than prepping for pro-ball??? I would say, have him use wood whenever he can.
My son loved using wood vs. bbcor for what I mentioned and he feels he gets noticeably more pop from a wood bat than bbcor. I feel sure if you were to ask him if wood bats helped him improve his hitting skills, he was say yes. And now that he's in his first full season of pro-ball, he's doing well and feeling very comfortable with wood.