[Dabhand16]

I'd set up in good time and speak to Father Christmas to see how he is going to work. Obtain permission to photograph him.

Use your tripod to keep the framing constant. Give FC plenty of room in the frame to allow for small movement in different shots. Doing this will make the shots quicker as you will not have to compose and focus every shot. Lens choice will depend on the space you have. Use between 50mm and 100mm if possible.

Depending on your location I would prefer to use bounce flash or side lighting with a reflector (or handy wall). Run off some test shots to tune in your settings/focus/depth of field/light position.

Try to get a decent distance between Father Christmas and the background. 6 feet and bounce flash will probably mean no shadows on the BG.

Set the camera to be at the kid's eye level and get all of Father Christmas in the frame - or at least all of the kiddie and top half of FC.

Use a remote release for preference or the self-timer if you have not got a remote.

Make sure you have a foolproof way of linking the pictures to the individuals you are shooting.

Make sure you have sufficient memory and spare batteries for the camera AND the flash.

Make sure you charge your batteries before the event.