Yes
Regarding purchasing for another family, I must admit that I am not sure. But I am pretty sure you can purchase tickets that are good for quite some time into the future (120 days if I remember correctly). The Kennedy Space Center website is pretty decent, easy to use and has a lot of information, perhaps you can try it out. I called them before my visit and I got a representative on the phone rather quickly and they were very helpful. Hopefully this helps you out.
Yes, if it is possible to buy it online.
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