You will be glad you chose DCA. It is physically easier there because it is generally shaded and there is an easy to spot line and no steps. Plus it is way more obvious where it is than at DL. The door to first aid is right next to Guest Relations also. Eyeball that, so you know where it is. Figure out what you want your first ride to be ahead of time because they will put it on your tickets right when they give you the
DAS. Also, I don't know how many in your party but I found it very helpful to get a lanyard with a clear plastic sleeve and put two tickets in the pouch, front to front. The tickets have to be scanned every time you want a DAS and this way you will not have to take them out. You do have do have to take them out to get fastpasses and there is a decent chance the plastic pouch will get separated from the lanyard at some point in your trip, so take a photo of the back of each ticket. If you can buy the clear plastic pouches before you leave, you will be glad you did. Sometimes it is really hard to find them in
Disneyland. Have a great time!