Hi,
I'll be pleased to complete this project for you. Let me introduce myself: I'm a CCIE (R&S) certified network and systems specialist with 7+ years of experience in developing, configuring, securing and maintaining complex networks for large enterprises.
I'm passionate about OpenWRT and have extensive hands-on experience with Coovachilli implementation on OpenWRT. Here is a Freelancer project that I successfully completed which used Coovachilli on OpenWRT:
https://www.freelancer.com/projects/php/Setting-Captive-Portal-based-openwrt/
Please send me a message so that we may discuss this further.