I would say stay clear of backing tracks. They have done for music what the digital camera has done for photography. Anyone can use them and create a half decent result... but few can use them to their fullest potential.

Backing tracks take away your chance to ad lib an audience. You have to be spot on your timing, ALL the time, and you have little leeway to interject anything verbal if you see something in the audience you could 'bring in' to the song. Of course, this is only my opinion, though I find being able to freely interact with an audience really game changing. You can hold off on a chorus while people get up to dance, you can repeat something, you can comment, you can mingle with others on the song (hearing mondegreens is great if you can repeat immediately with effect). You can also ad lib someting whilst someone comes up to join you. A backing track will never allow you such freedom.

I tend to cherry pick songs to fit a venue but I, by no means, choose all oldies and war songs for homes. Audiences have astounded me in the past with how up to date they are (being asked for Ed Sheeran recently and Sam Smith was an unexpected pleasure) and many like to join in. Being ol excludes no-one from such happenings and I sometimes ask the venue if any of their residents have requests for favourite folk, country or sixties songs.

I agree with never talking down. Just be ordinary and normal, treating them as an audience who knows what is going on, but be on the look out to include some of the folk who may be looking nervous or lost.

None of this is rocket science. Just enjoy what you are doing and the audience often enjoys it with you. Smiles go far further you may imagine.

Most of all...Enjoy! :)