Joe,
I do not know anything about the Indy Car experience, but can promise you that your Dad will thouroughly enjoy the Petty deal! There have been MANY open wheel die hards, do the Petty deal, and all walk away thrilled!!.. Promise.

As far as the cost, IMS costs Petty a lot more than the rest of the tracks, hence the higher cost than other tracks. Again, not knowing how the Indy Car deal works, w/Petty, you get plenty of instruction before hand, and ceremonies afterwards, which he should also enjoy. It is also recomended to do the ride-along before you drive. Yes, it costs more, but a whole bunch of confidence is gained from someone who has never done this, when they feel how the car sticks.

There is usually specials involved for folks that are with someone that drives, as they can usually get a discount to do the ride too... Be sure to ask ablout that before hand when reserving.

I am sure it will make for a memorable, and fun day for you and your Dad!