there's a Chase Sapphire Preferred promo for 50K going on right now, 3 months, 3K spend. Chase UR points are 1:1 transfer ratio to UA miles. Click
Here. actually, it's a 55K offer, but you'll need to add an authorized user too for the extra 5K points, which you may or may not want to do).
i think it's actually 6 pax (4 kids + OP + OP's DH), so there may have to be some searching for 6 award seats on the same routing round trip. so 210K for all if you can find saver. OP, if you haven't burned up any miles yet, you are most of the way there. the challenge may be finding saver award seats for 6 all on the same routing. at least you can get everyone into E+ if everything is booked on his miles due to his status.