Specifically make sure you can deliver exactly what these eager beavers are willing to sign up for, and that you can do it on time and within budget. They might've got the wrong idea, your mockups might've been too optimistic in their feature set, etc. Just make sure to re-validate your idea and confirm you are on the same page with these people.
Cheap - fast - good, pick two.
I need to start taking more detailed feedback from people but I don't want to sway them by asking leading questions.
Even though it only has a primarly and secondary features, it's certainly still beyond what I've ever built before.
I'm considering all angles really. Even if it means selling the idea on, I'd rather it get built properly.
Leverage this enthusiasm to build the MVP. If you don't know how or it's beyond your capabilities, there's plenty of resources available now to learn how. Get something in the hands of these early adopters and move on from there.