It would be really very helpful to know if you'll be taking inside or outside photos because the suggestions for each can be quite different! To me these are some of the key factors, whether taking photos inside or out.
Lighting: should be subtle and diffused; use available light especially if you must use a built-in camera flash (avoid doing so if you can).
Background: should not be distracting; use a large aperture for shallow depth of field (people are in sharp focus and background is out of focus). Oh, and make sure nothing is "growing" out of peoples head such as a tree, light pole or chandelier.
Clothing: like the background, make sure family members don't wear busy clothing, with flowers or strong stripes. Suggest that they wear clothing with colors in the same family or that complement each other (they don't have to dress like twins though.
) Also ask them to wear colors they look best in, but not too dark or too light so as to overly influence exposure)
Shooting: take LOTS and LOTS of shots of the same scene and increase the chance of getting good ones. Shoot at a time of day when, hopefully, the children are less likely to be tired and fidgety.
Oh, and take some test shots to see that everything looks okay.
Metering: Center-weighted or Matrix
Let us hear from you as to whether you're taking inside or outside photos; if you'll be using the S2 (like most built-in flashes, the S2 flast does only so-so); any information you can provide so we can provide additional help. In the mean time, these links give some information that can help you:
Tips for using a digital camera to take Christmas and holiday photos:http://www.digicamhelp.com/holiday-photo-tips/holiday-photos.htmDepth of field:http://www.digicamhelp.com/taking-pictures/depth-of-field.htmAperture:http://www.digicamhelp.com/advanced-digital-camera-settings/aperture.htmSlave flashes (for cameras without a hot shoe):
http://www.digicamhelp.com/digital-camera-slave-flash/index.htm
