Yes, if something goes horribly wrong and your seats get reorganized, you can call and have your family members put back in E+. Up to 8 companions of a 1K member, on separate reservations but the same flight, get free Economy Plus, per
http://www.united.com/web/en-us/cont...myseating.aspx .
Note that the
not-on-the-same-PNR part of this perk is not published anywhere but is generally assumed to be true. There have been occasional scary moments where agents have asserted otherwise.