First of all, only Golds and Plats are allowed guest privileges.

BTW, the last time I visited the lounge at BOS, the lounge staff had the names of all the pax entitled to lounge access. There is no EK staff at the Virgin lounge - so just by showing your J BP and Skywards Gold/ Plat card, I don't think it is possible to get a guest into the lounge. I can check and confirm this in 2 weeks.

Anyway, you won't miss much if you give the lounge a miss. Last time I went it there were a total of 3 pax in the lounge of which 1 stayed in the loo for most of the time.