While you don't have to worry about entertaining every single person, you should have a general idea of what the group as a whole will be interested in. A nursing home probably isn't going to hire a loud rock band to provide entertainment, but that same band may be hired for a 21st birthday party. That is not to say that your grandma doesn't like the rolling stones, or that a 21 year old has to like loud rock music, but we are talking about general terms.
When possible, I think unique entertainment is the best choice. People are more likely to remember entertainment that they don't experience every day. However, you may not want to try these ideas if you are dealing with a group of people who do not like change.
Murder mysteries are a great entertainment idea. You can even put on your own murder mystery dinner or weekend. However, if you aren't that creative, you can either purchase a whole mystery package including meals and overnight accommodations, or you can purchase just the script. Also, you can determine how much participation is required from your group. If your group is shy, you can get some volunteers to take on the more active roles or you can give everyone big parts if your group is more outgoing.
Karaoke is another great entertainment idea. However, with this idea you may have to go first to get things started. Sometimes people get the wrong idea that you need to have skill to sing karaoke so someone might need to set the stage for them.
The possibilities are only limited by your mind. You'd be surprised at what people find entertaining. Most of the time, unique entertainment may come in the form of a guest speaker. Find someone in fields that are interesting and have them not only speak to the group, but actually give them an interactive lesson. For example, you can have a striper give a bridal shower some lessons in strip tease. The possibilities are endless.