Depends on how much you want to spend, and obviously you know what your guests like, but we had a lot of fun last Xmas with a lucky dip made up of things from Hawkins Bazaar (
http://www.hawkin.com) - they have a range of games, puzzles etc that kept us in stitches long after dinner was over ... great for silly adults and older kids, but maybe not so suitable for tinies.
Little fun things from the Early Learning centre, or similar, for them ?
Big girls always like those small travel sizes of quality shower gel etc, so I get a Molton Brown selection from QVC. I'm afraid I've never cracked the ideal "man gift" ...
Alternatively, wrap up a small git for everyone. You're bound to find one at the table : ))))) sorry, I love typos !!!