I don't let my F/O's make announcements anymore because of the bonehead things I have heard over the years. But one neat thing we have at United is “channel 9” which is usually set for ATC. But when we near level-off and I turn the seatbelt sign off, I ask the pax to join me on channel 9. I talk about the a/c, who is flying, and several other aviation things that you can never talk about over the P.A.
So those who don’t want to hear anything from me don’t have to and those that do get more than they asked for. Neat feature.