We took a half day Denali Highway excursion and had two 4 door jeeps for our 7 person group. The way the excursion works is, they pick you up and shuttle you out of town to the launch site. The tour guide is in the lead jeep and the others follow, connected by CB radio. We drove about 55 miles down the Denali Highway which is a gravel road, stopping several times along the way for scenic views. The guide would periodically give commentary over the radio. While lunch is not provided, they do allow you to bring a cooler and they did provide snacks like chips and can drinks.
Pros: great views 'off the beaten path', personal attention, smallish group. Guide with a lot of local knowledge. Neat to drive a jeep.
Cons: quite expensive for a group of 7, road was very dusty which limited visibility (not their fault), we didn't see much wildlife (again not their fault).
At the end of the day, if you have access to your own vehicle you can drive this stretch of highway yourself, pull over at the turnoffs for pictures, and save a ton of money and time. At your own risk though...while not an 'off road' experience, the gravel does kick up when another vehicle approaches. One jeep got a windshield damaged this way. Take special care if renting an RV.