If I were to buy the $20 all-in-one pack would I be able to use the codes for my current account to get the mini-expansions? That is much cheaper than $30 for just the 3.
yes you can ^^
There's one code in the pack, use it to register any one of the expansions. Once you've entered the code, you'll be asked if you want to apply it to all non-registered services. Hit "HELLZ YES I DO" then enjoy ;)
If I were to buy the $20 all-in-one pack would I be able to use the codes for my current account to get the mini-expansions? That is much cheaper than $30 for just the 3.