Sorry, I'm still a little unclear on what you're trying to do. The widgets that you're setting up on customers' phones--are they map widgets? There is no actual Google Maps widget. When you say "widget," are you talking about the things you can place on a homescreen that you can interact with, or that have dynamically refreshing data (like a weather widget or a clock widget)? Or are you talking about the Google Maps app?
Since your customers have their own Google accounts, you won't be able to control their widgets. However, if you're talking about setting up maps to share, you could try creating custom maps using My Maps on the classic Google Maps interface on the web, and then sharing those custom maps with your customers. The tricky thing is that the customers would have to access those maps using Google Maps
on the mobile browser, because the current Google Maps doesn't support the classic My Maps feature. Here are some links to learn more:
https://support.google.com/maps/answer/62843
How to access My Maps on Android after Google Maps update - CNET