They threatened small claims court, and they already had lawyers, etc.

They are probably lying to you.

In general, lawyers are not allowed in small claims court, that's kinda the point. Sure, they can hire a lawyer to help them, but he/she will probably not be allowed during the small court hearing.

As you have nothing in writing, what's their complaint? That it doesn't "fence"? They don't like the way it looks? It was shoddy? Not secure? They can't just decide they don't like it and demand money back.

Take pictures, bring receipts if you have them. Small claims court only costs you your time + judgement. Let them sue you, show up and argue your case.