Have you considered ordering a pension file from the NARA? Military records at the archives often have family information. I found bible pages from a Larrabee ancestor who served in the Revolutionary war.
While the son may have gone to Canada, he wasn't necessarily a "loyalist," which is actually a term laden with meaning to those who are really into it. My Dad was born in Canada and we have loyalist ancestors, as well as relatives who were loyalist sympathizers and moved to Canada shortly after the Rev war. Through my limited loyalist research, I haven't seen any Larrabees, a surname I'm also interested in. (Which doesn't really mean much.)
The UEL mail list is a great source for not only loyalist research, but for any relatives that emigrated to Canada during this time frame.