A true "Ad-Hoc" network would not include networking infrastructure, like routers, etc.
If I'm following your question, you have a wireless Ad-hoc network setup, and you are using a machine to share an Internet connection with them (the "other pages" you speak of). This means you have an Ad-Hoc network, and a bridge to another network (the Internet).
It seems that what you want to set up is a "Captive Portal"
The machine or device that's acting as the bridge/router to the Internet is what will have to dish out the splash-screen before passing the info on, so it will have to be the host of the captive portal.
Wikipedia provides a nice list of Captive Portal software packages you could check out:
- Air Marshal, software based for Linux platform (commercial)
- Amazingports, Linux based software with integrated billing and payment implementing service-oriented provisioning, free and commercial
- ChilliSpot, open source Linux daemon [abandoned]
- CoovaChilli, open source Linux daemon based on ChilliSpot
- DNS Redirector, Windows based software solution (commercial)
- FirstSpot, Windows based software solution (commercial)
- HotSpotPA, open source Linux daemon based on OpenWRT, OpenVPN, and ChilliSpot
- LogiSense, Billing & OSS / Network Access Control
- m0n0wall, FreeBSD based firewall distribution
- NoCatAuth, Linux based
- PacketFence, Linux based Network Access Control software featuring a captive portal (open source)
- pfSense, FreeBSD based firewall software derived from m0n0wall
- pointHotspot a web-based Hotspot Solution, for any Chillispot or Mikrotik router
- SilverSplash, an open source ad serving captive portal for Linux platforms
- Sputnik, Software as a service solution (commercial)
- Untangle Captive Portal, Firewall featuring Captive Portal (Linux-based, free basic functionality, commercial directory integration)
- WiFiDog Captive Portal Suite, small C based kernel solution (embeddable)
- Wilmagate, C++ based and is executable both in Linux and Windows/Cygwin environments
- Zeroshell, Linux based network services distribution
- Hotspot Engine, Modified Linux OS, paid or a 30 day trial by request.