Magic Way tickets begin on the
day of first use. Unless you have the non-expiration option, you'll have day of first use plus 13 days before your tickets expire. Tickets have a fourteen day expiration.
Therefore, you don't even have to use your tickets on consecutive days!
So, it's up to your family which day works best for your first day in the Magic Kingdom, Epcot, Animal Kingdom and/or Disney's Hollywood Studios.
With the park hopper add-on, you'll be able to hop between the above-mentioned parks in a single day.
For instance, our family recently visited Walt Disney World with six day Magic Your Way tickets that included the park hopper option. We were there for 10 days but only visited the major parks on six of those days. We do not usually visit a park on arrival day.