Prince Edward Island - clamming, seafood, and what else not to miss?

Hello! So many of the PEI related responses are years old now so I'm hoping we might get some more updated information. We are celebrating my parents' 50th anniversary (7 years late) with a week with nearly the whole family (we will be 13 total) on PEI. My sons are interested in cycling, clamming, and eating seafood. I'm excited for all the L.M. Montgomery history and I heard we might be able to see a ceilidh? One of my nieces likes to surf and wondered if she'd be able to do that there. My mother and her sister (in their 70's and 80's respectively) are avid walkers. As a group we are pretty much game for anything but we also like to feel like we're getting a good deal. We are driving from Michigan's Upper Peninsula (with a stop in Montreal) and my parents are driving from lower Michigan so will have our own cars. Any suggestions for "must dos" and good spots for seafood and clamming are appreciated! Thank you!