How to best broadcast/stream rotating information to ~100 different TVs in different states

Hopefully this is the right place to ask this, if there's a better place please point me in the right direction

   

I work for a mid-size retail company with ~100 stores in different states. Each store has a TV with the following specifications

 

1. HDMI or USB. Sometimes both

2. None of the TVs are smart TVs

3. Each TV current hangs in the store displaying local channels

 

We'd like to

1. display a set of rotating promotions on each TV instead of the TV channels

2. This set of promotions would be controlled from the home office.

3. Ideally our marketing team would update one central file or interface and then have that update to each TV

4. Wifi is available in each location

  Something as simple as a the powerpoint being shown on each TV would meet the business needs. Is there any way to do this without spending an arm and a leg? For example, I thought of using a raspberry pie as a cheap mini-computer in conjunction with something like

www.rasplex.com