I've fished the whole area in a boat similar to yours for 15 years. [16' Skookum Sealer - completely open boat with a 30 hp 2-stroke]. Fishing from Port McNeill, the easiest spots are
1. along the shore towards Alert Bay [check your closed areas and times]
2. along the reefs that run from Ledge Pt to Haddington Island [again, check the RCA boundaries]
3. from Ledge Pt up to Lady Ellen and the bay above with gravel loading equipment
If you're up for going farther afield, the top end of Malcolm can be good, and then down the far side of Malcolm to Bere Pt and Black Bluff. There, you need to watch for the NW building fast, and be ready to get out of there quickly - its rough across the top of Malcolm if it blows up.
Even if its windy, you can often fish 1 above, or on the Malcolm Island side from Haddington Reef down towards Mitchell Bay. Whenever I fish in a boat like yours, I think about what it will be like coming home if it blows westerly. Eg. Lady Ellen is a great place to be if it picks up because you can run with it all the way to Ledge Pt, then you're inside the harbour and home safe and dry. Conversely, running back to PM from Mitchell Bay can be wet and rough.
If you're thinking of going even further afield, post again or PM me - I've been all over the Broughtons and fished out of TC and around Weynton Passage, etc. I'm not the best fisherman, but I know a bit about taking family in an open boat.