The scenario: Ann and Betty have been best friends throughout their adult lives. Betty stood up for Ann at Ann's wedding and vice-versa, each was at the hospital for the birth of the other's child, and so on. Each gets along well with the other's husband, and the two husbands get along with each other, so the two families socialize often, and spend birthdays and holidays together.
Sadly, Betty and her husband Bill are now separated, and in the process of divorcing. The split is as amicable as possible, and while one party made the final decision and initiated the separation, it isn't really anyone's fault. Bill has now started dating and become fairly seriously involved with someone else (Carol), although they are not presently living together. (Note that while Bill and Carol's relationship did begin soon after Bill and Betty separated, Bill was never unfaithful to Betty, and neither Carol nor any other third party had anything to do with the separation.) Ann and Betty continue to see each other regularly, both with and without their children and Ann's husband (Al). While Ann and Al socialized with Bill on several occasions immediately after he and Betty separated, they have not seen him socially since he and Carol began dating, and have never met Carol.
A milestone event for Ann and Al's daughter is approaching (think along the lines of first Communion, bat mitzvah, graduation, etc.), and they're planning a party to celebrate. What would be the most polite course of action?
1) Invite both Bill and Betty separately, but not invite Carol -- after all, she and Bill are not presently engaged or living together, so they're not really an official social unit.
2) Invite Betty, and invite Bill and Carol, as it's clear their relationship is a serious, exclusive one and they consider themselves a social unit. However, Carol should politely decline (concluding that a good-sized party with Betty and a number of Al and Ann's relatives in attendance isn't the best time to get to know Ann and Al) and urge Bill to attend without her if he wants.
3) Invite Betty, and invite Bill and Carol. Since Bill and Carol were both invited, they can attend or not, as their schedules and interests allow.
What would you do if you were Ann? If you were Carol?