If you marry, that spouses income is considered part of the family income…and in some cases, the step parent doesn’t feel they are responsible for paying for college. That second income would add money to you family contribution for college, regardless.
One other thing…at this point, you don’t know exactly what paths your kids might want to take after HS. One might decide that a trade (many of which are highly needed, and well paying) is a better choice than more classes. So…wait and see.