Hi Christopher,
Greetings from Hopkinton! I just sold a house in Framingham last month.
Anyway, you mentioned: "They are extremely needy and sometimes pushy tenants, and we don't want to renew their lease when it ends." Sounds like they gotta go.
How much longer does the lease have to run? When I was a landlord, I would religiously put tenants in under a written Tenancy At Will for slightly easier handling of situations just like this one. You might consider doing that next time around.
Anyhow, it seems that there is a lease violation. If you did not agree in writing to a modification, it seems like you'd want to serve them with notice that they are in violation, and that you wish to terminate the tenancy. In Massachusetts, eviction is a nightmarish, Kafkaesque labyrinth for the landlord. So before proceeding one step further, I would strongly suggest contacting an attorney who specializes in landlord-tenant law for advice and to help you avoid costly and time-consuming pitfalls.
On the plus side, Middlesex County now has two specialized Housing Courts (so you don't have to go through the District Court system anymore). The one in Marlboro is probably the applicable one for you.