as far as the door decoration magnets go.... no, they are not necessary, but they are one of those things that is very fun. I consider myself an "amateur artist" so made my own by drawing on the magnet sheets that you can buy. My kids loved it and it made me smile when I saw our door every time we walked up to it. You don't need a lot of time or talent if you want to make your own. You can find and print clip art online or find Disney stickers or paper decorations in the stationary aisle, wrapping paper or even deco at the dollar store that you can then glue to the magnet sheet and easily cut out around the edges and have something that will be very cute and add to your trip for not a lot of time or money invested.
A lot of enjoyment for me is in the getting ready part of the vacation, but this is one of those details that really carries over through the actual vacation time enjoyment. Bonus, bring the magnets home again and can stick them on the fridge or in school or work locker and have instant reminders and smile at the memories made on the trip.