Ina, I think you will be very happy with the iPad Air, and also think that the 64 gigs will be plenty. I have a lot of stuff on mine, and it is also a 64 gig, and there is still a huge amount of room that I have not used yet.
Since your books are on your Kindle, and your music will be stored in iCloud; you won't be using a lot of space for either of those. The thing I use the most space for on mine is for the apps, and then probably my pictures; but even some of them are stored in the cloud.
That is one awesome thing about the iPad, you will not lose any of your information because the iPad backs everything up to the cloud when you enable the automatic backup. I also sync mine with the computer every week, and that backs up files as well; so everything should be secure.
If you have a wireless printer, you can even print things from the ipad.
Both the iPad and the iPhone have a "hotspot", so you can actually use that for someone else to connect to and go online if you need that.
Mine also has LTE on it, which connects anywhere I am through Verizon. I seldom use that, but have used it a few times with the GPS program.
All in all, I am sure that you will LOVE the iPad. If you have any questions that I can help you with, email me.