If I only had 10-12 days I'd probably skip PEI in favor of spending more time around the Bay of Fundy (both NB & NS sides) & Cape Breton. While I did enjoy PEI National Park, the rest of the island was just kind of so-so to me. And, while driving to the island is free, it costs $50CA to drive back to the mainland so kinda pricey for just a day or two. There's also a ferry from NS but that's even more expensive ($86 per vehicle round trip).