I remember that that when I was in maybe 4th or 5th grade, so around 1982-3, I started reading a paperback book about spies in the American Revolutionary War. It had Benedict Arnold, and stories of other double agents. I think it was meant for kids (although it was still a reasonable sized book, probably at least 100 pages).
For whatever reason, I never finished reading it, and always felt a little guilty about it. I can’t recall the title or author, but I have a feeling that I’d recognize it if I see it.
Clearly the latest it could have been published was the early 1980s, but it certainly could have been older than that.
I remember seeing an entry for a book called “Spies of the Revolution”, in a catalog for the Arrow Book Club. I don’t think I ever read the book, but the catalog entry listed several of the spies profiled, one of whom was described as “a Boston surgeon”. This was in the late 1960s.
When I put the phrase “children’s books about spies in the Revolutionary War” into Google, I get a lot of books that satisfy that part of your description. I looked through them and didn’t offhand notice any that were from the 1980s or earlier and were about more than one spy. Try that yourself and look through the list you get. Perhaps one of them will be the book you’re remembering.
When I put the title Spies of the Revolution (which F.U. Shakespeare mentioned) into Google, I get a link to several books, including a 1962 book by that name (authored by Katherine & John Bakeless) which looks very close to your description.
If you like Spies of the Revolution, you might try to find a copy of Children of the Resistance by Lore Cowan, which is about the participation of (mostly teenagers) in the resistance movements against the Nazis in various countries.