Don't bring your mom.
If your mom is a ridiculously nice and selfless human being, it’s probably best to not bring her along to your trade fair. In fact, don’t even let her drop you off. She’ll see this as the official invite she’s after and kindly insist on walking with you to your business stand. From then on in you’re screwed. She’ll spend the rest of the day at the event in question, hovering around like one of those annoying flies that keeps appearing in your eye-line despite your many attempts to swat it away.
You may try and persuade her to go back home and leave you in peace, but bad luck, it’s too late. Nice, selfless, yet incredibly stubborn, now she’ll pretend that she wants to stay out all day at some soulless exhibition centre, when in reality she’s just so painfully desperate to be helpful, she can’t quite bring herself to leave the vicinity. (Well, you might need an emergency flat white, you see?)
This sounds nasty as the woman is only trying to be nice. But when you catch her for the third time walking past your stand as surreptitiously as Mr-bloody-Bean mere minutes after your last attempt to shoo her away, then you’ll end up more than happy to forgo free coffee – just to retain some level of independence if nothing else.