1st portrait shoot...Pricing...

I will be doing my 1st paid portrait shoot this coming weekend. It will be shot outdoors in a wooded area near my home. (actually in a private hunting/fishing club to which I belong as a member.)
The couple (sister of my daughter's wonderful boyfriend, Ryan, and her fiancee) has asked me to do their engagement pics after seeing what I did for Ryan (Sr. portraits). I shot his free of charge as a gift and due to the fact that he has to pay for most everything his self (no help from home).
Anyway that's how I was asked to do this.
Now I shoot sports mostly and dance pics. Non-posed pics 99% of the time...
I've read a few threads here and checked out a few sites...

In my area MOST photogs charge minimal sitting fees and what I consider HUGE sums of cash for the actual prints. These photogs do fabulous work and have a huge reputation in the area. They also sell image sets for thousands to the local grads. Esp. the females...

Now starting out in this type of photography I feel confident I can take pics the people will be more than happy with. But I really do not expect a lot of prints to be sold.
A number of the SM'ers seem to up the sitting fee ($100 on the low end to $500 or more on the upper end) but then charge less for the prints...
I think this is the way I wish to go... Using the same fee structure I do for events. $100 per hour and then post the pics for sale to the couple...

Any thoughts either way?

My basic pic pricing is on this page...
http://www.brandolinoimaging.com/gallery/1106521
Low end pricing .. maybe, maybe not... but I sell a few pics.. enough to keep me shooting...

Most of my money comes from shooting events candids for a local company that caters to high school yearbooks...

Thanks for any input...