Upload & Sell: On
It will be much, much cheaper and much, much more effective to redesign the site on a responsive platform than it would be to build a mobile app that most folks will never find. If your developer says different he is either overcharging you for web design work or has never designed a custom mobile app.
I just checked your site, which I tried to do from my iPad when I initially read your post. Your landing page runs Flash, which is a non-starter for a lot of mobile platforms and a lot of users (I block all Flash in browser even on my laptop, it's a security vulnerability). There is no way on earth I'd spend a dime on a mobile app before I updated that website.