Symphony primary focus I believe was on team collaboration within the financial industry. Yet, I haven't heard too much about it being used on the retail level except when someone violated the compliance department rules via using it for personal use. Also, for other programs...I highly recommend avoiding programs that also allows "computer remote controlling". I've seen a few people using such programs accidentally enable the "remote control" with someone they barely know and then the person didn't even realize it.
There must surely, these days, be loads of ready-made, very-low-cost solutions to this issue, and it ought just to be a question of assessing what's available, maybe reading reviews, talking with existing users, asking about the possibility of a "free trial", or whatever? I think there's almost guaranteed to be something which will suit you either perfectly or at least "close-to-perfectly"?
https://www.blizz.com/en/ Share your screen Present from your Windows PC or Mac, and collaborate with others on any PC, Mac, Android or iOS mobile device Show people what’s on your screen or share only selected applications Allows 300 people to see your screen.