If you really don't care at all where you eat, you could probably wing it and use up your dining credits. But you'll spend time finding places to eat each day. You may not like or care for the options available at that time as June is a busy month. If there is any place you really want to go or if you want to try a character breakfast, you should make the ADRs in advance. There are a few places that do not take ADRs but do take the dining plan like ESPN or Beaches & Cream where you can use up credits.
Personally, if I were on the dining plan, I would make ADRs just to have something in place and make changes as the rest of the daily plans come together. It would annoy me to no end to waste meal credits I paid for in advance.