Yes it can be used for both-you must call member services to use it to buy dining plan (can only buy online using a credit card) and you must purchase at least 48 hrs prior to arrival.
I assume you will buy your tickets in advance because of fast passes but one thing to remember is that the DVA cannot be used on property (must be done online or over the phone) so you must buy the park tickets ahead of time not at the ticket window.