Did a search nothing came up.

I'm on the same PNR with a fellow pax on a LHR-JFK. Timing for fellow pax is very tight, around 1hr at checkin before departure. I was thinking of checking in both bags myself (yes I know what's inside) so that fellow pax can run and do a checkin without bags.
Are they gonna let me do this? Do I need to split the (already e-ticketed) reservation first?
Thanks.