I agree... buy a LON-DUB ticket and fly from DUB... very slight chance you can get on at LHR on the outbound without problems.... even if you do (if all the systems don't sync up), the return will be cancelled when you get to the US.

If the 7-hr connection in LHR on the way back depends on whether it's overnight or not. If it's overnight, it's a lot easier to shortcheck bags. If it's not overnight, it's up to the agent at EWR.

If you don't manage to shortcheck them, and you don't show up for the LHR-DUB flight, chances are -- your bags won't travel to DUB without you, so they'll stay at LHR and it will be up to Aer Lingus to release them to you .