What are the overstay consequences for minors in Thailand on a volunteer visa?

Overstay question:

My family is here on a one year multi entry volunteer visa, so we all have to exit every 90 days. My husband just returned from a work trip outside of Thailand, but my kids and I need to exit on/before June 12. We are leaving Thailand July 11 for several months. Wondering if I exit solo in the next few weeks without the kids, (kids all under age 9), what’s the overstay consequence for minors, with the overstay just under one month?

We can all head to the border in a few weeks if need be, but since my husband doesn’t need to, just wondering if we could save a road trip with young kids, just me exit and return, and then all of us leave July 11 without much issue?