We used Tiffany in July. I had a coupon from the back of the Passporter, but there is one you can print out from Tiffany's website. Our driver told us summer is actually a slower time for them since so many people drive during that season. Their busy time is October. So, yes, I would book today. And if you want the grocery stop, which is complementary, make sure you state that when you make your reservation up front. We had a very positive experience with them.
Have a magical trip!