Purchase E+
Given that you are travelling with small kids, I would not risk waiting to the gate. Depending on the flight, there may be no E+ by that time. Better to purchase the E+ supplement for the kids and have all 4 of you together or don't purchase and have them move the 2 of you back to E- (or figure out whether there may be seats in E+ and E- close enough for comfort.
Remember, E+ doesn't do much for small kids because all it does is give you extra pitch.