Welcome to FT, bailey76, and to the US corner!

While paying to upgrade an award ticket is not possible, you could perhaps think about buying a ticket (any Economy fare class, except W or S IIRC, is upgradeable transAtlantic) and asking your folks for an extra 10k Miles each for a possible upgrade (30k each way per pax). It's based on availability, and sometimes you may not be able to confirm the upgrade at booking. Of course, buying the more expensive Y or B fares gets you an Envoy upgrade for only 10k each way, and upgradeable at booking too, but I don't think many vacationing pax do that.

Don't know where you're flying from, and in which time frame, but transAtlantic fares should be more of a bargain as cooler weather approaches.

Best wishes for a good trip!