Marriage is a vocation, sacred to God. So you have an obligation to form the best marriage you can.
If you're a young man (under 35), keeping yourself as best you can from being soiled by the world, then you should only accept a pious virgin younger than yourself.
If you're not keeping yourself from sin - then you should work to improve and then find a virgin to marry.
If you're an older man, like over 45, or have already made serious life mistakes (you have children, or a long history of fornication, were previously married, past abortions) then you should consider women who have made similar mistakes and are also trying to recover. That would include a woman, younger than yourself, with children.
The further you have strayed from God's plan for a Christian family, the more you should accept this in a woman's past.
But you should only consider a woman who understands these previous choices were wrong. Of course she should love her current children - but her attitude should still be that it would have been better to follow God's plan - and a commitment to follow it in the future.