Captive portal without nodogsplash

I would like users that connect to one network land up on a splash page / information page. No internet access or anything needs to be enabled for them, just that they see some information on a page served by openwrt.

I would also like to run this on the central openwrt router rather than needing to install something on to the low RAM APs on the network.

I have setup vlan that would route requests to the potential splash page. If I understand it correctly I would need to:

  1. tell dnsmasc to answer all connectivity check hostnames with the IP of the router (is there a way to do this on a per-subnet way?)
  2. setup a virtual host on luci/httpd that listens on port 81
  3. a redirect rule that captures alll requests to port 80 on the captive network and redirects them to <routerIP>:81

is that it or am I forgetting a step? Would this kinda work without all the complexity that NDS adds?