Can I designate my children as my beneficiaries in a will if I am legally separated since 5-06 in PA? Ex continues to fight settling divorce.

Unless the separation agreement specifies that you must name and maintain a specific beneficiary (such as your spouse) for your life insurance, you can name anyone you choose.

One potential issue is what happens if the beneficiaries are minors? The insurance company can not pay minors the proceeds until they turn 18 so the proceeds are typically held at interest by the company, or paid to a court appointed guardian of their property. But in either event the money is typically paid to them all at once at 18, which many people believe is too young for a person to get a relatively huge sum of money all at once.

That's why people going through a divorce often set up a trust for their children, naming someone other than the spouse as the trustee, and designating the trust as the beneficiary of the insurance policy. In that way at the discretion of your selected trustee (say a brother) some of the money can be used to meet the kids needs while they are younger, some can be used to pay for for a college education or home, and the rest given to the children on attaining milestones, such as some at age 18, some on graduation from college, some at 25, etc. rather than the children getting it all at 18 when they may be as likely to use it to buy a fancy sports car as productively save or invest it.