In addition to the Expedition there are a couple of other options in the smaller 46-53‘ range...the Voyager and Adventurer.
I’ve never rented them but whenever family or friends ask me about Powell houseboat rentals, and in your case especially for an extended trip, I recommend checking out the “Boat Specs“ at LakePowell.com for these often overlooked items:
Engine size/hp & Gal/Hr fuel consumption. These “Economy” boats usually come with either a single 3.0L inboard or a pair of 60 hp outboards. The single 3.0L inboard is slightly more fuel efficient but two outboards offer redundancy in the event of a mechanical issue and better maneuverability in/around docks. Neither engine option will set any speed records but will tow your Tracker just fine and get you to EC in 5-6 hrs.
Holding Tank Capacities. Obviously the bigger the Black & Gray water tanks, the less time and fuel ($$$) you’ll spend moving around to empty full holding tanks.
Generator Fuel consumption. Gensets can range from 4KW to over 10KW with widely varying fuel appetites. The higher the KW the higher the Gal/Hr, meaning more expensive fuel you’ll have to pay for when you turn the boat back in.
Some boats have all-propane appliances while others have household-type 110v appliances that require daily generator time to recharge house batteries. The propane refrigerators are pretty ineffective in the hot summer months but work pretty well when highs stay at below 90F.