The slowest recommended handheld shutter speed is 1/60s, but like many others above have said, an even faster shutter speed of 1/100s to 1/125s is infinitely preferable - just even to capture the image at the correct moment and to avoid say people blinking.
Regarding the correct focusing, if you choose AF mode then your camera will choose the closest object/person, it might be a good idea to try Live View next time (pops the mirror up too), then hit the zoom button twice so you get 10x magnification, then focus in on the person's eyes who is sitting in the middle. Then take your shot. You can also select an optimum aperture (often f5.6 to f8) for your specific lens and keep the ISO at 200 or 400 when shooting even well-lit scenes like this indoors.
Finally, one simple trick often used by Pro's and enthusiasts is to switch to Hi-Speed shooting and take multiple shots in succession, that way you can minimize any handshake effect, as you'll have several exposures to choose from (then delete the OOF ones in-camera)