Okay, so I went to
http://epgy.stanford.edu/for-parents/epgy-open-enrollment/register
and clicked on "Create New Group", and filled out the form with a parent and our DCs, so our group is our family. Then I emailed info@epgy.stanford.edu to request SSA credentials for our group/family (it's not automatic when you create the group, but you just have to ask for it after). Alternatively, you can join a group that already exists.

Our DCs haven't started using it yet. But I have explored the SSA account and played with the settings.

You/SSA can change the setting to "gifted" (this applies to K-7 Math only, not LA/Wr or Alg).

But another setting that I'm guessing will speed things up is (for each subject) in "Session Settings" have "Review exercises* (0-15)" set to 0, so you don't have to start each session with a bunch of review exercises (unless you want to).

The "Math races" are optional. You can set (session) "Duration* (10-300)" to 300. There are a bunch of things that can be set.