Are you actually on a Non-B visa or on an extension of stay? Look in your passport. If you are actually on a visa you need to wait for it to expire, you can't cancel it and you can't simultaneously hold 2 visas. If you are on an extension of stay you should cancel your work permit then take the document showing you've cancelled your work permit to immigration to cancel your extension of stay, then go apply for the DTV
there have also been instances where people have been denied the visa because of this or have had to immediately fly back to their home country to get it issued. Luck of the draw.
Get your visas sorted before you come to Thailand but if you don't have a residence visa for Egypt you won't be able to apply there. Your husband can apply for a 90 day Non-O visa based on being over 50. You could possibly apply for a 90 day Non-O visa as his dependant as could his kid up until he's 20, but this depends on the consulate you will all apply at. You can't do this inside Thailand. Depending on his pension income it might also be worth looking at the LTR Wealthy Pensioner visa in which case dependants aren't an issue
If you already got your 90 day Non-O visa in Chiang Mai you must have a bank account with the required funds in it. It should be a simple process to get the 12 month extension of stay, just visit immigration and ask for their requirements