I think if any child wants to play music it is our job to encourage. Whether they do it for enjoyment or a career is not important. I grew up with young man called Frank Gambale and as a teenager he used to say one day he is going to play with Chick Corea. Yes we used to say OK right.. Frank but look where he ended up. If you visualise the experience enough it will happen.
My own son Jacob wanted to be a drummer like me and we encouraged it. He ended up going to a really great school here in Australia and ended up playing with the top tier of Australian Jazz musicians by the time he was in his early 20's. Yes it has been hard for him too, getting work and surviving but now he is playing on a cruise ship with a great band and earning great money. He plans to move to New York next year.
So it may work that way for them or not but the main thing is they are playing music for enjoyment.
Like I said if he wants to play bass get him a bass and let him go for it. It does not have to be a huge expense either. Yamaha make nice bases that don't cost the earth. They are handy to have around even if they don’t follow up on it.
The greatest gift
Dave has given to his son is simply being a musician. I have been a successful musician for the last 36 years surviving as a full time player and composer. If you want it bad enough and can visualise how you want it to be hard enough it will happen.