You (every foreigner, regardless of what type of visa/entry) need to submit TDAC, the application window is from three days before until you enter (are stamped in at passport control at your entry point to Thailand).
So, you are going to apply for an initial in-country Non-O visa based on marriage to a Thai male. You can apply for it anytime now, as long as you still have
*****
days (depending on your local office) remaining with your current stamp.
if you have an actual Non-O or Non-OA, it cannot be transfered, you bring both passports until you apply for a new visa or an extension.
if you are alraedy on an extension after an actual visa, you can transfer stamps to the new passport.
bring both passports to enter thailand, show both passports when you are stamped in and be sure you get correct stamp on your new passport based on the extension and re-entry permit on your old passport.
you go to the local immigration office once you are abck in thailand to apply for transfeer the stamps.
Canadians and Vietnamese can enter Thailand on visa-exempt for 60 days. All need to have return tickets, proof of accommodation, and TDAC submitted. Also, as a rule, one of you has 40K in cash for the whole family.
You may need an original consent letter from the parents of your brother. Both parents must sign.
You need to contact your airline for details about a minor's travel by international flights. Those details are out of the scope of this group.
Sadly, your online reporting window was between 9th and 16th July (both dates included). You have until 30th July to report in person at CW. Keep watching the result and cancel it before you go if still pending.