You can go, but from experience your documents may not be sent back in time. If you have an urgent need to travel before the under consideration stamp date, then this question needs to be raised through the Immigration office where you initially applied.
You need to be married certainly before you apply for a visa (related to marriage to your Thai wife). In my case, we were married in Feb 2016 and did some travelling. I entered Thailand May 2016 on a 60 day TV and during that 90 day period (60+30), I applied for the 90 day non O visa. Before that expired, I then applied for the 1 year non O visa (subsequently extended on yearly basis since then).
you werent sure it was 18 or 19 when you looked.....short of going to Immigration or back to the IC at the airport to clarify, how else do you suggest it is resolved?
if they apply for the covid extension and get denied, will they get a 7 day to leave stamp in their passport? if so, will this affect future travel to Thailand?