Choose a time and date when all the family members will be available. Coordinate the calendars and plan accordingly.
Set a theme for the photograph. You could all decide on making the same pose or totally different ones. Be creative on this stage and also take tips from other family members. For example, all the members can carry writing boards with alphabets wishing the holiday to those receiving them. Such creative ideas can liven up things and make the card stand out. The dress colours can be coordinated to give a more aesthetically pleasing and planned outlook. The dresses could both either be complemented or be contrasted according to your preference.
On the day of the photograph taking, check your camera and its settings in advance. Use the manual for help or any experiences friend for help in getting the right settings so that the photograph is perfect. The settings will depend on the light exposure and background etc. Use camera tricks to make the photograph more creative.
Rehearse the positions with the members. Who will stand where and next to whom? What will be the poses and the expressions? Coordinate the heights and make sure that everyone is getting the right exposure.
Since you will be a part of the photograph being a family member, place the camera on timer settings and rush back to your designated place. The timer should be long enough for you to settle down. Take multiple pictures so that you can select the best one out of them. Use photo editing software to enhance the effects. Take a print of the photograph and build it into a holiday greeting card with wishes from the family.