SI,
I was browsing my bookshelf (well, one of them) for something to read while lifeguarding my son in the tub and my eye landed on "The French Soldier in Colonial America", a booklet Rene Chartrand did a while back. It has a section on the canonniers-bombadiers and their ordinance. Aside from the uniform details which I think you have covered he does verify that the Ministry of the Marine was responsible for all ordinance in coastal fortifications and the colonies in general so the guns were of the standard naval design of the day. The calibers were standardized at 4,6,8,12,18,24, and 36 pounds. He also mentions marine mortars which were not standardized, but most commonly found in 7-, 8-, 9-, and 12-inch sizes. Sadly there are no pictures of these potentially useful pieces.
I'll include this quote which is a useful summary. "The guns sent to the colonies were often pieces which were considered too heavy or too old for use on warships. They were painted black and mounted on wooden garrison carriages painted red. Colonial gunners also used a few light pieces on field carriages."
Pretty general info, but I hope there is something useful in there for you.
Aaron