Thanks. I guess I am concerned with the founding team not seeming hardworking enough to succeed.

I think I may just end up doing that as a test. Thanks again.

You should just say that directly then. Something along the lines of...

"Us founders are blitzing 80+ hours a week. If you're young and energetic, come join us. However, we'd also like the wisdom and experience of someone more senior. We understand you have a family and will need more life balance, and we're very cool with that."

I'd find that refreshing in a job ad. I'm 42 with a family, btw.

I have a family and wouldn't reply to that ad at all

"Our team is passionate and growing quickly. Perks include a healthy work/life balance."

Meh "a healthy work/life balance" to me is a pre-condition. If you use that phrase with the word 'perks' in the same sentence I'm moving on...

That wording doesn't sound very attractive. Down right scary actually.

Which part? The 80+ hour a week part, or the wanting people with family part? I think the OP's point was that killing yourself at a startup is a young person's game, and he still wants to hire people more experienced people with families who are looking for ~40 hours. That would unusual in many startups, so I think it is worth mentioning. How would you say it better?

  "Us founders are blitzing 80+ hours a week."

This is where most people with a family would stop reading.

  "If you're young and energetic, come join us."

That is border-line ageist. The rest is a half-hearted apology that won't entice a normal person to want to work in the advertised conditions.