Internet Cafe Setup

I'll be helping someone to setup an Internet Cafe and would like some inputs from you experts.

Features of the Cafe:
6 Windows Stations with Internet Connectivity
Clients will be able to print to a network printer
Wireless connectivity
Internet Cafe software to monitor station usage

Network layout:
DSL/Cable Modem goes into a software firewall box (Linux). Firewall connects to two networks.
Network 1 (private/Local): 6 Windows stations (Windows), Internet Cafe software server (Windows)
Network 2 (DMZ): Wireless access point, print/mail server (Linux), may add a web server for the company (wouldnt take much bandwidth)
Firewall rules: block smtp (reduce spam), network 1 can go to network 2 (for printing), network 2 cannot go to network 1 (Internet Cafe software server contains sensitive data like company record/customer credit card number and stuff).


Policies:
Anyone on the network send a print job. However, customer has to talk to a staff to release it.
Wireless network is open.Not going to use WEP or other securities, since it's too much trouble for the customers and staff to set up.
Desktop stations charged by usage time.
no smtp relay. Has to sign up and use our smtp server.

Questions:
1. Who should be DHCPd? Only the firewall, or server in network 1 and server(s) in network 2?
2. What program would support the release of print job in Linux?
3. How is my current email setup? Would it block most drive by spammers?
4. What kind of wireless access point should I get? Should be able to handle 30 or some simultaneous connections.
5. What program in Linux is good for throttle bandwidth (by host)?
6. What would be a good Internet Cafe software? Customers can pay before or after use. Program has to be able to lock computer when timesout. Integrated with POS. No need to lock down the computers since we'll be using deepfreeze to protect the stations.

Any help is appreciated. Thanks.