I have 2 x SC5000’s 1 x Prime Go and 1 x Prime 2 all on the same account but they are never used at the same time.
I have had issues in the past with 2 x SC5000’s if you open a lot of songs in quick succession you sometimes get an error and have to wait a few mins before trying again. Not had it for a while tho.
So I suspect tidal have some sort of limit on unique devices that can connect in a set period of time, you would have to ask them.
Im sure if they saw lots of connections from different devices in a different locations it would cause you a problem, if you are out gigging £10 or £20 a month is a small amount to pay per DJ so I would just pay up to avoid any issues.
Edit: How Many Devices Can I Use Simultaneously? – TIDAL
I suspect you may get away with it on a family account.