I'm going to guess that Marcus lunged at your husband because of his quick movement and alarmed state, more than any attempt to keep your husband from picking up Beaker.
I agree with Birdhouse. It would be fine to give the boys an opportunity to see if they might hit it off, but be sure to supervise, especially if you are going to trim Beaker's wings back. I have also read that Greys don't tend to be very sociable with other species, but every bird is an individual.
We have a variety of parrots which cohabit our bird room, and most of the time they are out loose together. So there is a parrotlet, a pionus, several conures, medium cockatoo, and sometimes a lovebird loose together in the room. I think it works out because they are all flighted and can easily approach or retreat from each other, as needed. I would not feel at all comfortable with them all having unsupervised access to each other if they could not fly. Given this arrangement, several relationships have developed between various birds, especially the sun conure and the cockatoo, who are BFFs. Our Grey does not live in the bird room, and so far, has not been very friendly toward any of the others and vice versa.
Usually, dissension between our birds occurs when one of the humans is present and jealousies are aroused. This is something you will have to watch for when you bring your birds together. These kinds of jealousies are also the reason for many nips and bites directed toward the humans. For example, my sun conure loves me, but does not like the Grey. If I am holding the sun conure and make any move to approach the Grey, the conure will nip me hard. So be careful of this type of redirected aggression if you try to bring your birds together.