We have never been asked about our children in all the years of doing my extensions based on marriage, and probably just as well as they are 33 and 25 years old and both live in Australia. Children don’t matter when it comes to extensions of your Non O visa based on marriage
The money must in your account 2 months prior to your extension, each office will require different things, but Phetchaburi also requires a copy of your bank book pages to show this as well.
If you mean a fixed term account, where you cannot have access to your money until the fixed term expires, the answer is no you cannot use this type of account, as immigration says you must have access to the available funds.