Can you really come to Portland without seeing a lighthouse? Absolutely. Should you? Sure, why not. We came here on our second date after seeing a show at Empire together, and neither of us wanted to leave.
Hopefully the wedding will fall right at leaf peak, so getting out for a hike that weekend is something we highly recommend. Pleasant Mountain is about an hour from Portland but the view is definitely worth the drive. You can even jump in Moose Pond when you come down if you're feeling brave.