Definitely the 2 X *G

In addition to seating (each UA *G) can bring one other person into E+
YOu'd also have international *A lounge access (for 4 total if travelling together) and extra bags for both *G passengers (6 total).

With Plat- you'd get the E+ also, but just lounge access for you +1 at foreign *A lounges.
Plat would give you a few more fee waivers and better upgrade prospects domestically...but I'd def go with 2X *G if the perspective is for the benefit of the whole family.