Sizing for videoconferencing solution

Hello everyone wanted to make a query

I have a central office and 3 branches.

I'm thinking about buying:

- (1) Polycom RealPresence Group 500 + License MCU
- (3) Polycom RealPresence Group 300

This solution would work?

I have understood that the Group 300 does not support MCU, but if all calls the 500, should work?