That all sounds good though I would recommend Naxos over Mykonos in March as there’s more to see and do there when not beach weather. And if you do decide to do Mykonos be sure there’s a ferry from Mykonos to Santorini for your dates. And same for Santorini to Crete. There should be ferry service but the route starts different times every year so you do want to be certain.
We are having trouble deciding on another island to go to besides Santorini (we both want to go there). I was hoping you might be able to make a suggestion. We are not really into late night partying/night life. We LOVE good food..quite possibly the most important item on our list. We also like to hike, my husband is very into history, we love beer/wine, we could definitely be into in a less populated/touristy type spot. Gorgeous beaches and great views are also a plus.