[CentOS] pointers for using CentOS box as filter for children

greetings

has anyone here setup a CentOS box to use as a home or business gateway for
children through young adults or otherwise?

i realize this is a generalized question and that iptables and many other
things exist that could be implemented.

im looking for a way to give the youngster the benefit of the doubt and
allow them to "obey God/parents" first before they have to be totally
restricted after having been disobedient.

specifically we could do it two ways.

one is, that which is not expressly permitted is denied... and i would
prefer not to have to do it that way. it is too easy and may not allow for
the child to choose to be obedient to God/parents.

the other seems like it might be better, that which is not expressly denied
is permitted... YET

i want to make sure of only a few things if possible...

how can i keep the youngster from using an IM program and how to make sure
they are not transferring files larger that say 100k, ie no large music
files etc? only small pics or homework things etc.

can one hit a moving IM program protocol port target that recognizes the
packets and shut it down?

also, what packages out there are people using that have time based
restrictions, like until 11pm or other configs?

thanks

 - rh

--
Robert Hanson - Abba Communications
Computer & Internet Services 
www.abbacomm.net