Remotely update apps through MDM

Hello, we are developing a kiosk app for iPads that will run in single app mode in retail stores. The ipads will be supervised. Since our advertisement app is not related to the public we can not put it on AppStore. And we are a startup we can not register to enterprise developer program (since it requires having 100+ employees ). So what is the proper way to manage these devices remotely and install app installs remotely without user interaction? We will use MDM to remotely update apps but should it be an enterprise app? Or up to 100 devices can we remotely update using ad-hoc distribution through MDM?
Another option is Custom App which lets you deploy apps to affiliates and partners without registering as an enterprise. But I couldn't find whether custom apps could be remotely installed?