For your first time I would definitely say YES!!!! One thing to note is - the tour (like most tours) can be quite tiring, so I would say it's a MUST to do the tour BEFORE the cruise, not after. As the previous poster says you can then rest on the cruise.
We have also done 3 Alaskan cruises and the one Cruise tour. The cruise tour gave us such a yearning to go back and explore Alaska that we took our RV, from Florida to Alaska and spent 5 months there ... it was off the charts unbelievable!!
Now I would absolutely only rent a vehicle in Alaska and do it ourselves. It is so easy, not congested like the lower 48. To the person who said they would be afraid to overtake a slow RV - firstly the RV's travel at the same speed as the cars, don't forget you're not doing interstate speeds. Also it's no problem to overtake a RV because most of the time you have the road to yourselves and there isn't oncoming traffic for miles. The only busy places are Anchorage and Fairbanks.