Just a fantasy hockey GM posting here.
I wouldn't worry too much about the ELC, especially if the kid can be a useful player for you this year. The big thing is the 40 game limit, which would make him a FA faster. It's not possible for him to get there (unless they count playoff games?).
Anyways with the way RFA signings have gone the past year (Kuch, Lindholm, Trouba), don't sign, don't play. I wouldn't worry about paying him a large sum in the near future. And when the time comes that you have to pay up, it'll be after many years of productive hockey for you guys, at which point, can you really complain?