We did a similar trrip a couple of years ago. We used Brimley sp as a base camp. It worked fine but you will for sure need something farther west if you are staying in the porkies (haven't been there yet but its on my 'list'). Brimley was perfect for the kids. Its a bay that is shallow forever and its the warmest part of lake superior so the kids could swim too.
If you get to pictured rocks, take a kayak or a boat tour. We had a 2 year old, sos did the boat tour. Its 3 hours and is amazing! You might need a reservation if its a weekend. We went on a weekday in july and it was pretty full.
And I second the restaurant antlers in the soo! So good and we still talk about it!