Ecuador is full of beautiful places and there are lots of fun things to do. It is always difficult to advice someone else of what to do when you don’t know what they are interested in. Rics writes that you should avoid Quito, but I love Quito very much and will definitely spend a few days there during my next visit to Ecuador. Taste is personal.
You say that you choose these three places because they were recommended by Lonely Planet for a one week visit. I presume that you then have looked at photos and read about things to do in those places and feel that they are good places for you to visit.
Your suggested itinerary is the opposite of what I suggested. Have you read the posts in this thread carefully? I advise you to go back and do so again! As I wrote in a previous reply I think it is better to do a daytrip to Cotopaxi (if that is what you want to do) in the end of your trip, because of the altitude.