Money is actually the least of the problems. If you are older, you anyway need to plan that you might be out of job for at least one year. Unfortunately, for programmers, if you get older (40+) it is very hard to find a new job in same field due to ageism. So either you take control of your destiny or you pray.

So if you are in 40s and worked for big corporations as senior engineer / manager you should have about 100K in savings (assuming you save save about 5K a year of your 150K salary).

Regarding kids, yes that is a big responsibility but also something you don't get tired doing.