Hey Girl! When you went to that site to set your account safety to "Adult", were you logged in to your account, or the Primary Account of the Family Plan? Also, is your account a child account by itself (usually under 18 years old)?
Regarding you purchase of those map packs, any account should be able to use them on that same console, but the purchasing account will need to be logged in to LIVE if you want to use it on another console. Let us know about the questions above and we'll make sure we get everything squared away for you. Thanks!