Hi Art!
Thanks for your question and for visiting the Disney Parks Moms Panel!
Visiting
Magic Kingdom is such a wonderful experience that you can't possibly see and do it all in one day, but sometimes that's all there is time for. And better than not coming at all in my book!!
There are a variety of
Park Tickets available in both day count AND options, such as park hopping.
Since you are using a single day ticket option, you can enter and exit the Magic Kingdom on that given day as much as needed. For example, if you wanted to leave for a swim, or to visit Disney Springs, or to head to a nearby resort for lunch or dinner, there is no limit on the amount of entrances and exits.
I hope this helps and I wish you a Magical trip!!
Chris