The best attraction in Amesbury is Hodgie's Ice Cream, where you can order by the quarter-kiddie or half-kiddie. Brave the small if you dare. I'm pretty sure the place is a mafia money laundering operation, because they clearly aren't making a profit selling ice cream that way.
There's good pinball and people-watching a bit north on Hampton Beach or Salisbury Beach. You could also get a very scary tattoo.
I always recommend the Lizard Lounge show, regardless of who the feature is (AHEM my '06 Cantab teammate, AHEM) because the Jeff Robinson Trio is a completely awesome band. They really know what they are doing when it comes to backing poets. If you aren't into the Lizard scene, though, you can always head west to Worcester for the Sunday night show.
slamnews.com has all the pertinent info and links. Or you can drop me an email; I'm out of town (hello, Seattle!) until 7/5, but I'm happy to answer questions or make suggestions.
Have fun and please don't hestitate to contact me. I'm sorry I won't be in town to welcome you.