These are indeed trying times. Now sympathize with these GAs as they try to deal with people who misunderstand the rules or are otherwise misinformed. Your inflated and incorrect expectations make it no easier on them.

You should have been able to upgrade only one of your companions for 5 certificates each on the IAD-SEA leg. It is unclear whether your upgrade was cleared or whether it was waitlisted, but since the upgrades are pulled when you check in to First, it seems likely that there is some detail that you are missing or misunderstanding here, since it would have been impossible to pull 3x6 from your account. I also find it highly unlikely that all three of you would clear on a Sunday transcon.

As others have stated, UA does not preboard families. I think your compensation is due for what seems to be a misunderstanding on the GA's part for the number of e500s, but I would be happy with what you got. The GAs were already bending the rules in your favor by trying to upgrade the three of you as a group and clear you as a group (when you should have cleared on the merits of your own status).