Hi Michael, and welcome to CruiseCrazies!
I'm not sure if you mean this summer or 2022 (no Alaska this summer), but both ships pack a big punch. Quantum class is the newest class of ship and the more technically advanced. It's known for North Star (the arm with the attached pod), Sky Diving simulator, and is very popular with teens and young adults for the activities they love. The Oasis class (Symphony) is the biggest ship at sea, and has a staggering number of bars, restaurants, and entertainment choices. Their claim to fame is the Flow Rider, Aqua Theater, waterslides, and their "neighborhoods". Both ships have more than plenty to do for your family with young kids, but I think the Symphony would be a good fit if you don't mind traveling cross country.
Let us know what you decide!