Universal Annual Passes

I am planning my 2016 trips. I am not sure that I will stay for more than two or three nights at Universal and although I most likely will be purchasing a Disney Annual pass I have questions regarding the Universal pass. First, when I look today it seems that a 3 day pass is $130 less than an annual pass. If I buy one I can then purchase my son’s 3 day pass at 15% discount? If my sister and her family travel with me can I buy hers too? I also will be able to apply a room discount? Finally, do I have to wait until January to purchase it ( I know it says it is activated at use but can I purchase now for April)?

Here is a TP Blog post that discusses the various benefits of a Universal AP, including additional ticket discounts, room discounts, etc. http://blog.touringplans.com/2014/07/23/shocking-savings-universal-orlando-annual-pass/