I am planning on installing a new electric water heater. This water heater is to serve 3 ½ bathrooms and a family of six (4 adults and 2 children). What size should I be looking for?

The average home has a 40 gallon water heater in it, however, I'm going to give you a link that will calculate the capacity that your family will need.
WaterHeaterSizing (http://www.blueridgeemc.com/WaterHeaterSizing.htm)
Good luck, Tom