First, if you would be tempted to have an abortion simply because the insurance pays for it, I would definitely say you must not take that insurance. Then it would be an occasion of sin for you.
I doubt the above is a consideration. So you are probably worried about your possible material cooperation by paying funds into a company that uses some of its incoming funds to pay for abortions. In considering material cooperation you should think about who, if anyone, will be hurt or led astray by you having that insurance.
Would your son/daughter be more likely to get an abortion or more likely to think abortion is okay if you have this insurance? By not purchasing that insurance, could you prevent the people they insure from having abortions? Will your failure to buy the insurance change the hearts of the insurance executives? Things like this. If it seems to be that no one will be injured or led astray, then I think it becomes an issue for you to discern (your free choice).
If there is some risk of hurting someone, here are two types of considerations. If you only save $10 and there is a slight risk that your daughter will be enticed into abortion, then it would be a sin to get the insurance. It would be unjust of you to run that risk to your daughter for $10. On the other hand, if you think your buying the insurance could distantly encourage the executives to keep up their ways, but the money involved would impact your family needs, then it may be fair to get the insurance.
I hope that helps. You may need to ask an apologist, and not on the regular forums.
