I think a frank talk and a "hobby account" is a great idea. I dont think you are probably spending too too much and I dont think he is really really overconcerned. But retirement (consulting) is a different animal emotionally probably more than financially and you each will respond to the change differently.
I know when my parents first retired, my Dad fretted and my Mom didnt. Now that my Dad is 83 and in poor health, my Mom is fretting and my Dad is not. Really financially their picture hasnt changed only the way that each perceives it.