There's a Dunkin Donuts across the street from the boathouse.  Do you really need anything more?

If you do, the boathouse is 5 minutes from downtown Lowell where there are many fine dining opportunities.   As any local for a recommendation, or just head to Cafe Paradiso for pre- or post-race carb loading of the finest quality.  Reasonably priced.  If you need to spend more money, heda to La Boniche.