casual rehearsal dinner in York-Portsmouth area
With 60 people, you would almost need a banquet hall or something large - like Cliff House or Harborside (Formerly the Stage Neck).
If you want fun - sports bar, pizza, pub style - then definitely call Fazio's in York - also the Inn the Blue's might be able to host - you would basically rent them out.
Lastly, the Dockside is in York.
Now if you come south - then you have places like Redhook can handle 60 people, Gasligth might be able to do it - especially if you did it upstairs and then could have the dancefloor, etc.
I would call the Chamber Of Commerce for Portsmouth and York - they have a meeting planner guide which might give you a bunch of good leads.
Both my daughters got married in Maine. One got married at nubble light and had her reception at the york harbor inn. I give it a 5 star rating because the staff is superior and food is good. The other got married and had her reception at clay hill farm in cape neddick. I also give 5 stars to clay hill for the same reasons. Both places are pricy, but well worth it. Cliff house and stage neck were very difficult to work with, so I do not recommend either. good lock philly