You should have no problem at all. Male rats are quite good with younger males. In fact I often use one of my older or retired breeder rats to run herd in a feeder/grower bin. The mature rat helps establish a social order in there and keep the young rats from being hyper. Calm feeders eat more, run off their body weight less and in my larger rat bins that's important for me.

Just like anything though Justin, keep an eye out at first and just see that the big male is doing fine with the smaller ones. Individual rats can react out of the norm just like any living creature.