i dont see it as a too late or not. more about a risk management issue, especially with kids. They cost money and time. Startups require significant time and doesnt provide much money (in early stage).

can you do it on the side of your day job ? can you financially afford not to have a day job ?

About the age thing, a fun way to considere it is not "they are young and im old", but more "they are inexperienced and i am experienced" :)

and another thing, find at least one partner who is business savy. This is a requirement