On the issue of child migration

You can apply together, of course, you must provide the birth certificate that these two children are your own children.

You can apply

300- unmarried couple visa. Valid for 9 months, Australia can transfer to a temporary spouse visa after marriage.

If married in China, apply for a 309- temporary spouse visa. The validity period is 2 years. If the marriage still exists after 2 years, you can transfer to 100/80 1 green card.

Children transfer to green cards with their mothers.