frankfurt airport to amsterdam?

i will arrive in Frankfurt airport in the night with 6 person of my family so can you advice me the cheapest way to travel by bus from Frankfurt airport to Amsterdam. As i lookup the train is very expensive to travel with all my 6 people.
I am in a low budget. 3 adults and 3 children below 12.

I checked on the German rail planner for you, and they have a ticket for 322,80 EUR but with a savings fare for 195,00 EUR, that is 3 adults and 2 children, as the system did not let me enter a 6th person.
Check if one of the children is below the age when they need to start paying.
I think that is at their 6th birthday.

You can enter your details in this page, hit enter or click on search and on the second page you get you can add your ages, yours and the children:
http://www.bahn.de/p/view/international/englisch/international_guests.shtml

Here is a link for the bus:
http://www.touring.de/index.php?id=229&L=1&zort=AMSTERDAM&zland=NIEDERLA NDE&sland=DEUTSCHLAND&SP=EN
http://www.touring.de/index.php?id=2&L=1