Parkhopper tickets only give you one magic morning, and it is available only at
Disneyland. It's on Tuesdays, Thursdays, and Saturdays. The only way to get early entry to DCA is to stay at one of the three on-site hotels, DLH, GCH, or PPH. If you stay onsite, then you can use early entry every day of your stay at whichever park is offering it each morning. DCA early entry days are Mondays, Wednesdays, Fridays, and Sundays.
If you are considering visiting Minnie's during magic morning time, you probably want to use up your magic morning first. For one thing, you don't want to waste that special entry time eating breakfast. For another, if you are going in early just to eat at Minnie's but you haven't used your magic morning yet because you're trying to save it for later in your trip, it still may be marked as used at the gate when they scan your tickets. I haven't really seen a clear answer on this.