yes, we rented canoes and carts.  we used Bear River Mercantile.  There is also Becker's, and the "park operator" rents canoes too, probably a concession runs the park?

the portages are easy other then the length, and other than the 2nd portage.  two people, one at each end of the canoe should have no problem single tripping the portages.  On the downhills, it can be hard to hold back the boat to keep it from running too fast and bouncing off of rocks or roots and tipping over - one of our group did tip their canoe over once. 

If you do choose to double carry, there are big steel bear proof food lockers at each end of each portage, and at the two trails as well.  Every camp has several of the food caches, so you don't have to hang or hide your food.  If you were to do this with an ultralight boat and not use a canoe cart, the food caches make things easy when double tripping.