They're all going to be on their final years of their contracts. Acciari will have value to a playoff team. We're not fans, but players and coaches love guys like him and his contract is much more palatable for one year.
Similarly, a contender might value Hayes for some bottom six offense and overall reliable play, especially a team that plays at a slower pace.
Heinen is the one that could be a challenge, but with the rising cap, he could be a fill-in third liner on a non-playoff team if that team thinks it's going to struggle to work a deal in free agency for a similar player.
EDIT: Heinen could be in one of those draft day trades where some team calls the Pens and wants to move up five spots in the fifth round because some scout has a hard-on for a specific guy. So the Pens say, OK, let's swap picks, you take Heinen, and we'll take some 25 year old fringe ECHL/AHL guy just to balance out contracts.