The REAL middle ground could be something like a small business which doesn't require insane amounts of time to run, so that you can still raise your kids. You might not make it to a billion dollars, but boo hoo.
I'm at a growing startup of almost 100 employees. In my 2 years there I've repeatedly heard the CEO bash our partners' "lifestyle businesses" for their lack of ambition. These are companies of 20-30 people where the founders are pulling in 300-500k a year without working much more than 40 hours a week. Ironically, if our upside game flops our company would devolve to exactly the same thing.
This is a fantastic middle ground as far as I'm concerned and I'll be very happy to take a stab at this myself after I feel that I've learned all I need to know from working for the man.
Yes... that's why I flippantly mentioned flipping a house, which isn't a business as such but can be used to make money on the side where the money isn't linked to the time you spend.
The middle ground is to buy an existing business and/or invest. Yes booooooring! but lots of parents start businesses.
Flipping a house is a viable alternative to starting the next uber.