I've said I hardly take them to shops and after yesterday's experience I won't again.
But you should. You really should.
It's that simple. It's no disaster. Your kids were a pain in the ass while your back was turned while you conversed with another assistant. Let me tell you...so what??? It happens. You know now if you were to repeat that situation what you'd do differently. That's all that's needed here.
You got a second assistant who was stroppy in how she pointed out your kids were being a pain and that didn't help. Only you know what caused her to say "you shouldn't be allowed out in public" because that's a really uncommon thing for anyone to say, and you'll know exactly what made her say it, even if you're not alluding that to us. Again....so? She was rude. You could have handled it better. Lesson learned.
The answer isn't, at the first criticism, hide indoors. You must see how ridiculous that is. There's lots of things you can do.
As a mother of a SN child, we can't use that as an excuse. It's certainly not an excuse for people to judge our children. It's equally not an excuse to pretend their behaviour is acceptable because it's what you're personally used too. People will comment on unacceptable behaviour, because they don't know it's not their fault, and they think you're allowing it if you're doing nothing. Yes, we'll get more looks because people look at behaviour that is different to what they're used too. That's just life. My friend's son has autism. If she had a pound for every time a random has said "control your child." What she does do, is just look directly in the eye and reply very non aggressively, "He has autism.". People back off very apologetic and red faced almost immediately.
You know what works best for them. You say you hardly ever take them in shops. Maybe that's the issue? Take them in more? Let them not get excited by it.