My 43 year old son is got to have surgery on his hand for radial palsey in his hand what can we expect to happen after the surgery?

Depends: It depends on the cause of the radial nerve injury and the length of time it has been present. He will need several weeks to heal, extended physical therapy with a skilled hand therapist, and, hopefully, in time, he will regain strength in his hand. Nerves can regenerate but do so very slowly: 1-2 years.

Tricky surgery: Three nerves serve the hand: radial, ulnar, median. Ulnar trouble gives you ring/pinkie numbness. Median trouble gives you carpal tunnel sydrome. Radial trouble gives you pincer problems. Hopefully, this is a straightforward release of a compressed nerve in the arm. My expectation then would be that he would have recovery of whatever function he has lost as a result of this nerve being insulted.