You need to have a software development process in place. Agile methodology is one of the most popular at the moment. It links product features to actual code released in fixed periods of time (iterations or "sprints").

Using this framework, product owners can get an estimate for each proposed product feature and manage available resources (developer's time in this case) accordingly.

The most viable option is hiring an experienced software project manager (part time), who can get development process on track, so that you can concentrate on managing business, not IT. Alternatively, you can assign additional responsibilities on one of developers to standardize and oversee your development process.

If you have any questions, don't hesitate to contact me, I'm sure I can give you a lot of good insights.