Guided up there for 3 summers, the routes you could take are endless, best to get a good map and plan it out. Two main places to get in are Gunflint lake and all the access points around Ely (I suppose you could enter from far west near the NP too..) When I guided I aimed for ~10 mile days to keep you entertained. Portaging takes a while so any day where you are carrying a lot maybe whittle down the distance.
Fishing is spectacular, mosquitoes are also spectacular but the beauty makes up for it. My recommendation is to get further into the center of the park as soon in your trip as you can- fewer people and better fish. From Gunflint I really like the granite river route and from Ely I like going east as far as you can although west (through Basswood and Crooked) has fewer portages and more paddling (and more people)
Ahh, I miss it so much! Take a few fishing rods and a mosquito headnet!
"Paddle silently, boof loudly"