One way to help is to make it a very welcoming activity to the women as well. For my Mother's Day Champagne Brunch, it had an even mix of both men and women. According to some of my residents who attended, they wouldn't have wanted it any other way. They were able to share a very emotional day with the friends they have come to respect and adore. They felt having their friends there with them, male or female, made their celebration more enjoyable.
However, if the activity that you planned is based around "Male Bonding", which is perfectly okay...like Karen said, have open arms, however it is okay to tell the ladies that this is a "male oriented" activity. You can even label it on your calendar or bulletin board that way so everyone is aware of your honest intentions to honor the men in your facility.