YOUR UNDYING LOVE & DEVOTION, JUST BEING WITH THEM IS MORE THAN ENUF...
but anyway .... it will always go down to material things; so for your wife her favorate perfume with body lotion is good enuf, if she loves bags, jewelries, display in the house... depends on how you know your wife you can choose with the above...
for kids which are really easy to pleased ; chocolates, PSP, or whatever thery are interested into...
FOR WHATEVER, YOUR PRESENCE IS ACTUALLY MORE THAN ENOUGH THAT MONEY CAN'T BUY ;)