Voice Synthesis Options for Video Tutorials? (TTS?)

Hello,
I have been asked to help create videos of basic computer tasks. Think along the lines of creating a folder on a desktop and renaming it.

There will be a number of people working on an ever growing list of videos with the goal of uniformity in the overall “branding”. I figured different voices with different microphones will render this a disaster.

Text-To-Speech enters the picture.

The org is a charity and they need to keep expenditure low and if I can find a suitable free TTS program that works well for short tutorials whilst also sounding professional, that would be perfect.

If free and professional is not an option, then can you recommend a best “bang for your buck” option? I would have to justify all costs and show it’s 100% necessary, so if the gap is large enough and the price is small enough, then they would allow it.

I have seen Amazon’s Polly and it’s surprisingly inexpensive qualities, but now isn’t the time to take a swing at this, as time is of the essence and they want to keep things very simple.

I appreciate any input - thank you!