If I have an SD card with 3DS games on it, will putting it in a camera or laptop delete the games?

No it will not delete the games unless you tell your camera or laptop to format the SD card. So be very careful about what your computer is asking you to do when you plug the card in.

In a laptop it will show up as a storage device which you can access and copy the files from your SD card to your computer.

Beware: while putting it in any device besides these with desktop OSes as some of them tend to silently format cards if they cannot read them for some reason (be it wrong filesystem or anything else)

As long as you use a reader directly connected to Windows device it will be fine (or Windows will ask if you want to format if anything bad happens), but cameras, phones etc are risky; consult a detailed manual to be sure (but unfortunately details like this may be omitted anyway).