D30 Flagship Lounge and the E Concourse Admirals Club are not that far apart due to the fact that you can go to D31 and use the cutover to E, the lounge is on the right once you exit the cut over, ,next to E5.
Lately many of AA's LGA flights have been leaving from Concourse E, I have no problems using that lounge, in fact the "adult beverage" selection there is better than any of the D lounges.