How can I convert my dependent visa to a longer stay in Thailand?

Hey all, looking for a little insight. My husband is working in Thailand with the appropriate visa and a valid work permit. My kids & I recently obtained our 90-day dependent visas in Vientiane. We now need to convert them to multiple-entry, longer stay depdendent visas at the Chiang Mai office.

1. My husband’s current work permit is valid through June 30, 2020. However, his contract with his employer states that he will be working for them through June 30, 2021, and we intend to stay that long. Am I right to assume that they will only issue dependent visas to us through June 30, 2020? I often hear it referred to as a “one-year” dependent visa, but they won’t give us a full year (yet)?

(1a. If, for some reason, we were eligible for full year visas, my 3-year-old daughter only has 17 months left on her passport, not 18. Would this be a problem?)

2. Every day, my husband goes to work and my kids go to school. I’m bored. I would like to at least volunteer someplace. I’ve been given conflicting information about whether a non-imm O dependent visa is sufficient for legally volunteering. Is it? If not, what would the process be? Because I might as well try to do that instead.