Using Airport Utility > Internet > Internet Connection your Time Capsule can be configured to:
- Share a public IP address in this mode it creates its own independent network by providing DHCP and NAT services to any device connected via wireless or the ethernet LAN port(s) on the back.
- Distribute a range of IP addresses which is similar to sharing a public IP address but without the protection and flexibility of the NAT services.
- Off (Bridge Mode) which means the TC creates the wireless network but provides no DHCP or NAT services and relies instead on the router for the ethernet network.
I gather from your description you wish to use option C and let your
beloved software router handle all the routing and I presume DHCP as well as NAT chores.
IMO a better choice for your network would be to choose option A and allow the TC to create the network and provide all the DHCP and NAT services for the wireless network and any devices connected to the TC's ethernet LAN ports. Your
beloved software router would still be providing the routing services for your wired network. I have a somewhat analogous, albeit less complex network here that is configured the way I suggest and it works beautifully. Any wireless device can "see" devices on the ethernet and
vice-versa even though the wired and wireless networks use entirely different IP address ranges. I think you will find this works better.
That may or may not solve the issue with the children's PC laptops connecting to your wireless network however. There are a lot of variables and especially if you are using 802.11n networking the
draft final standards are not due until 2010 and although there are a lot of 802.11n devices on the market, the devil is in the details. Not all 802.11n devices or devices using 802.11n in b/g compatibility mode are in fact compatible. If that is the case you may need to back down to 802.1b/g only for connectivity with the PCs. You will also do better if you can use WPA and not WEP security but WPA may not be available on the PCs.