Unlike Facebook or twitter, it is not obvious in Google plus how to send private messages. It requires a little bit knowledge on how Tricks work there. In Google plus, you can choose who can see your text messages.
You have greater flexibility than Facebook messages.
In Google+, you can choose individual person or circles and give access to your message. If you choose one or more circles and give access to your messages, all members in those circles can see your message.
Following is detailed How to send private or personal message in Google+
First type your message in Stream, and type the name of the person or circle with whom you want to share that message, you can select multiple persons or cicles.
This is how your message can be visible to all those person u want.