I've only been to
MVMCP once ... but we opted to have a "late lunch" (2:45ish) at Whispering Canyon Cafe (at the Wilderness Lodge) and then head over to MK to get in with our MVMCP tickets shortly after 4PM. (We planned, and spent, the morning and afternoon relaxing at our resort.)
Our plan was to maximize our MVMCP tickets and spend the hours before 7PM doing rides etc. (We ended up needing to go back to our resort first, and got to MK around 5:30. Nevertheless, having the late lunch worked out better for us than an early dinner would have - had we opted for dinner, we would have gotten to MK well after the party started.)
Having the buffer time between our ADR and the "official" start of the party was nice.
Also, since CM is a buffet, if you're not on the dining plan, lunch is less costly than dinner I think.
In terms of being hungry later on that night, we just made sure to get our snack of cider and cookies and we were fine.