Insurance assessment
I think that insurance companies have a good idea of risk. When i started to learn to fly last year I rang my insurers to see if my new activity would have an impact on my life assurance policy in terms of premium, cover etc. They were pleased to tell me it wouldn't, I would be covered for private flying with no additional cost - they sent a letter to confirm this.
If the insurance companies (who are putting their money where their mouth is!) are not fussed about the risk of private flying then tell your father he shouldn't be!