The very important question is, how much days/weeks do you have for your holidays on Cape Verde?
That might rule your plannings for your island hopping.
To visit more than one island and to enjoy it, you should have a fortnight for your stay there at least.
Flights ought to be booked the earlier the better!
First decide, what are you expecting from the islands (only beaches or also hiking in the mountains, or to climb upon an active volcano), and then begin to book flights and little pensions.
There are numerous pensions on all islands.
I wish you a lot of beautiful days and interesting experiences.