I have done a Greek Islands cruise, but I did the 10 night on Celebrity. You will be hitting 2 of the islands that I visited. The Greek Islands so far is my favorite cruise to date. They are some of the most Beautiful places in the world. (I have some Photo's framed in my home that I took of the Greek Islands), The Greek food is great, the local beer is great and the people are warm and friendly.
I think you picked a great first cruise. Good Itinerary. I have not been on the Jade, but on her sister ship the Pearl and enjoyed it. I can suggest The Blue Lagoon for a quick bite of breakfast without the lines of the buffet, also good for late night snack. The French restaurant and steak house are well worth the extra cost. You will have a fantastic time being spoiled on a ship and seeing the islands.
I'm looking forward to your review and some posted photo's when you get back.
P.S. Have a Volcanic rock filtered beer for me on the Islands.