Couple things to add...
I've done my own TPIR show for the American Cancer Society for the last five years. When I began, on Randy's advice, I called Fremantle's business affairs office and asked about permission. I was told I could do it as long as I followed two rules: 1) Do not call it "The Price is Right", and 2) Do not personally profit from it. So I call mine "Game Show Night", and I donate 100% of the gross to ACS. I don't even take out my expenses.
As for the Showcases, you could do what I've done. I play it just like the show. Two showcases, with furniture, cars and trips (all fictional of course), and the Showcase winner gets the "Grand Prize Showcase", consisiting of the real prizes we have (over $1000 last year).
The quick way to make sure everyone knows that is to have a brief half-sheet disclaimer for contestants to sign as they enter the auditorium and get their nametags. This way, everyone knows it's for fun and the prizes are fictional, and as the host of the show you can still play it straight, as if you're giving away cars, cash and trips!