Even though Harry was 49 he was still in decent physical condition. He made it a point to take daily walks, usually a few miles. He was by no means a frail, elderly man. Of course he wasn't some sort of big, tough, could probably live to 90 and still be able to race around, type of guy.
At the mention of the invitations he smiled, and asked, "Who're you inviting to your wedding?"
Well one guest was already taken care of when Heather handed him his invitation. He gracefully accepted his invitation, "Thank you very much Heather."