I may be going out on a limb, but instead of joining a credit union before your trip, why not join Chase. Then you could use all the ATMs at WDW and DLR fee free instead of trying to drive around to find a credit union ATM.
Larry
That's what I did -- sort of --
Knowing that Washington Mutual and Chase are now one and the same, I opened a WaMu account (when they were offering one of their "cash bonuses" for opening a new account --after their meltdown and subsequent takeover by Chase) for the sole puprose of "non-Disney use" (since neither WaMu or Chase has branches in my local area).
Plus, as the debit card has MC/Visa branding, I can use it offsite, should the need arise...