I hate to say this, but generally the less questions you ask the better. When I got married in Newport the event planner wouldn't let us do a vodka toast (my wife's family is from Poland) because they considered it a "shot". But then the bartender was serving my underage family Jager-bombs all night long.
As long as the bartender is in charge of all the liquor, then just supply him/her with the beer and don't make any waves.
FYI - after a quick glance over the RI General laws, I only see the following statute that addresses homebrewing. I'm not sure if there are any other regs tucked away that cover your specific situation or not. *Disclaimer: I am not an attorney, but I've been known to watch Law & Order on occasion.
§ 3-1-3 Manufacture or sale of cider and manufacture of wines and malt liquors for domestic use exempt from title. – Nothing contained in this title and chapter shall be construed as to prohibit the manufacture of cider, or the sale of cider; or the manufacture of wine or malt liquors for domestic use.