Would you suggest putting together a tour on your own? We've cruised Alaska before, but when we go next with our kids (first time was pre-kids), I want all of us to experience more than just what was done on the ship. We live on the East Coast, so a trip out to Alaska is a major undertaking.
You could put a tour together on your own. The tour operators used by the cruises are available to book by anyone. However, the cruises do book a lot of stuff so you want to plan early to make sure you get the tours you want. A lot of tours you can't just show up and expect to get a spot. For instance, halibut fishing charters (or any boat tour) can book up for the whole summer by early June. Plus, lodging outside the cities can be very hard to find without reservations. However, with some research and planning you can skip the cruise part and just see Alaska.
Many people drive RVs up there, but this requires an extensive amount of time. It can take a week or more of driving, each way. Flying into Anchorage is pretty easy, about 4 hours from Seattle. Anchorage has the best selection of flights. You could fly to/from Fairbanks, but flight options are more limited. Alaska Airline operates a lot of flights to both Anchorage & Fairbanks. They are a pretty good airline.
There is really so much to do. You can do glacier exploration, fishing, gold mining, etc. Denali alone is a few days. The hardest part is narrowing down adventures to meet your allotted time and budget. Keep in mind, Alaska is very expensive and the tours aren't much cheaper on your own vs. going through the cruise ships. The operators have to make all their money in 3 months and demand is usually very high. So prices are expensive for most things. However, some planning can allow you to take advantage of early booking specials. Driving in Alaska is easy, if not boring. Renting a car is the best way to see the most on your schedule. Keep in mind, stuff is quite spread out. From Anchorage it is a few hours drive down to the Kenai where you find fishing excursions and some glacier tours. Fairbanks is about 5 or 6 hours to the north. However, Denali is right on the drive between those 2 large cities.
There is much to do and you can do it on your own. Many people who drive RVs set up their own itineraries. But advance planning will help you immensely.