I *think* that you can take a guest into the first class lounge at DXB IF you are travelling first AND have a Gold card.

That is the impression I had when my colleague (the B***ard) booked himself first and me biz and I went to the first lounge to meet him; they checked if he had a gold card and refused me entry as he did not (I did have gold).
As already mentioned, you can both use the Biz lounge anyway and you should be Gold Card now (or very close) with that number of first class trips on EK.

Of course, 'guest' refers to anyone you want to take into the lounge whether son, husband, mother, business colleague whatever.
Hope you enjoyed your flight regardless.