Hello! You'll love playing SOTMK! I highly recommend getting a case beforehand as the only one available at WDW is huge and, in my opinion, a pain to carry around. We go to WDW often and our trusty, compact Monster binder has held up amazingly well and has kept our cards safe and secure. Search
Amazon for "Monster Binder - 4 pocket trading card album" and you'll find it.
Collect as many cards as you can...
As I'm sure you already know, you can pick up a free pack of cards each day, one pack for every person playing the game. So even if your whole family doesn't actually "play", I recommend you all sign up for it so you can get your maximum allowance of packs. There are 5 cards per pack and they are SO fun to collect! My kids had a blast with this when we first started out.
You may want to purchase a few special cards in advance....
There are 70 cards to collect (well, technically there are 12 collectible party cards as well, bringing the total to 82), but the free packs only offer the first 60 in the collection. The last 10 can be purchased in the SOTMK game packs (although you'll get only 1 of them per game pack). The game packs are available in The Emporium on Main Street and also at the Trading Post in Frontierland. You can also purchase those last 10 cards individually, as well as the party cards, on Ebay. If you think your children may be keen on collecting you may want to buy a few of these special cards in advance. Fair warning: the older the party card, the more expensive it is. Party cards are only available during Mickey's Not So Scary Halloween Party and Mickey's Very Merry Christmas Party, which is why they are expensive and hard to get a hold of.
Feel free to message me with any other questions! I'm more than happy to help.
We are huge SOTMK fans and have spent a lot of time playing and learning all about it.