While OP's post contains many irrelevant points, with more than 3 hours of transit time, OP him/herself should be able to make the transit without issue.
Note:
1. With a party of 4, having GE is practically irrelevant as you have to wait for those without GE.
2. Having UA Premier Access is also irrelevant. First - *G matters more (as it determines how fast the baggage will be offloaded from SQ). Second - although tight, TBIT (after exit) to UA gates within 30 minutes is do-able.