Aparents - how would you like to be approached and when?

I would appreciate ANY help on this. I am 15 months into reunion with my son. He had his aparents blessing with regards to looking for me (a good start). After initial contact from my son and our first meeting 4 weeks later, I wrote to them to consider their feelings and I believe I have been very careful with their feelings and my son reported back that they were very pleased. I've had one letter from his amom when there was a crisis and she signed it "love... (name)". I think of their feelings by not phoning him at home where he lives with them, that kind of thing. I would however, now like to move things on and I'm wondering, if you as an aparent felt that the bmom was being sensitive to your feelings too in the reunion, WHEN would be a good time to ask to meet? HOW would you like to be approached, what would get the best response from you? I imagine meeting up on neutral ground, or perhaps even at the adoption agency that first brought my son & I together at our first meeting. I see that my son has been very argumentative with his amother during the reunion and I feel I understand what has been going on, and I have made certain responses to him to alleviate it, so hopefully his aparents can now see a calmer, happier young man and hopefully the arguing is calming down too. Any thoughts whatsoever would be so appreciated.Thanks in advance.