Yes. Everything you want to do is possible.
Q: I am currently an Xbox LIVE Gold member. If I have time remaining on my current subscription, do I receive a discount on an Xbox LIVE Gold Family Pack?
A: We will give existing Xbox LIVE Gold members a prorated discount on the purchase of a Family Pack. For each month remaining on your current Xbox LIVE Gold subscription, we will reduce the purchase price of a Family Pack by $5. For example, if you have six months of your Gold subscription remaining, you qualify for a $30 discount and will only be charged $69.99 at the time of purchase. If you have 20 months or more of your current Xbox LIVE Gold subscription remaining, you can upgrade to an Xbox LIVE Gold Family Pack for free. You will not receive a refund for any remaining subscription time in excess of 20 months.
Q: Can I add existing Xbox LIVE Gold members to my Family Pack? For example, my kids are already Xbox LIVE Gold members.
A: Yes. When an existing Xbox LIVE Gold member is added to a Family Pack, the remaining time on their Gold membership benefits the whole family! For every two months remaining on their current Gold membership, the entire family receives an extra month of Xbox LIVE Gold. For example, if your child has six months remaining on their existing Xbox LIVE Gold membership, when you add him/her to your Family Pack, all four of the individual Xbox LIVE Gold accounts available in your Family Pack will be extended by an additional three months. If you have two children who have four and six months of Gold remaining, respectively, on their existing Xbox LIVE Gold subscriptions, all four of the individual Xbox LIVE Gold accounts available in your Family Pack will be extended by an additional five months.