We did Alaska on our own this summer (end of May into June) and were quite successful at staying within our budget. We rented a car at Hertz at the Airport in Anchorage ($30.00 per day) and drove to Denali. It is a 5 hour trip, but the scenery is really incredible. We also saw lots of wildlife along the way. We stayed at the Denali Princess at Denali - and were very disappointed. It is definately NOT worth the price for the accommodations. The Grande Denali had just opened and is perched on a hillside. The views from there are quite spectacular and the rates were great at that time ($99.00 per night until mid June their flyer said). Their food was also much better than any we had anywhere else in Denali. As for the park, we arrived just before Memorial Day and were able to drive all the way to mile 30 in our private car. We saw lots of wildlife the two days we took this drive as there had not been much traffic at that time and wildlife was more active. However, the wildflowers had not bloomed at the time either. We took the bus to mile 56 the first day it ran (Saturday) and were stunned to see both mountain goats and a moose on the side of the road giving birth (it was incredible!). We also saw a brown bear very close to the bus and got great photos.
From Denali we drove to the Kenai Penninsula and stayed at the Kenai Princess. I wish we had planned more time a the lodge since the accommodations were great. In late May it is still cool at night, so we had a fire in our own fireplace. From there, we went on to Seward and to our ship.
While in Denali and in Cooper Landing (Kenai Penninsula) there were scores of people on the Princess land tours being bussed from place to place. We came out way ahead of the Princess rates and were able to travel at our own pace. We stopped at Wal-Mart north of Anchorage 'just to see' how the prices would run and were surprised to see the prices the same as in the lower 48. One thing - soda products in Alaska come from Canada - not the US, and are NOT the same. As an avid diet coke drinker, I will remember this next time as I went 2 weeks without 'real' diet coke.
Just another note, we received several e-mails from a travel service in Talkeenta (I found them at Alaska.com) and found their knowledge of things to do and places to see to be very good. We booked a float trip and air service through them to see Mt. McKinley and were very pleased at the rates and service. You might look in to this.
Have a great trip.