The bus tours into Denali are fairly inexpensive, but you are there to enjoy the scenery. The park is so big and there's so much to see... if you only there for one day, the bus tour is about the only way to do it. Just know that it is a school bus, so it's not especially comfortable. The chances of seeing McKinley are slim, but the chances of seeing wildlife are pretty good.

Driving to Homer is also a pretty good drive--in the opposite direction from Denali. As Flyski mentioned, the drive to Portage Glacier along the Turnagain Arm is about as pretty drive as I've ever been on. If you are looking to go down to Denali AND the peninsula, I might recommend going to Seward. It's a bit closer than Homer, and has other things to do there--Kenai Fjords tour, fishing, hiking, etc. It is also a cruise port, so it might be more crowded than Homer. (Although Alaska will be crowded in general this time of year.)

Anyway, I served my mission there, and spent a week on vacation last year, traveling between Seward, Anchorage, and Denali. With a night in Kodiak thrown in. BM me any questions, and I can give you some of the lodging recommendations and info.