For 25 cents you can buy your kids a handful of fish food. I usually give them an empty Dunkin' Donuts bag that I have hanging around in the car, but of course that will not work for you unless you are also a slob. It's helpful for them to have a container, is my point.
Rainbow Trout swarm to the surface at each nugget of food. It's fun. Often you will see Herons, Eagles, and plenty of hawks and gulls. During part of the year the holding tanks are covered with nets to keep the birds out, but you can still see and feed the fish.
This is a relatively quick activity - don't plan to spend the day! We are usually in and out in under one hour. Sometimes we go in the really cold weather and spend 15 minutes. It is only a quarter, after all.
Biggest surprise about this place: It does NOT smell. Seriously. A faint odor sometimes, but not fishy.
Parking is free.
There are no restrooms.
Sunderland Hatchery (my post)
Massachusetts Fish Hatcheries