Toilet, Bathroom or Potty?

As many of you know Ellie is almost 5, going on 15.

She has an endearing habit (not) of shouting at the top of her voice 'I NEED THE TOILET'.

After receiving several strange side looks in restaurants and supermarkets when she declares her need I decided that we had better work on our phrasing so last weekend just as she had screeched out her need for all to hear we had a little chat - it went something like this...

Me: Ellie, I think that perhaps it would be more polite while we're here in America if, instead of hollering at the top of your voice that you'd like to use the toilet we quietly ask instead if we can go to the 'bathroom.'
Ellie: Why? A toilet is a toilet Mummy and it doesn't have a bath in it at a restaurant.
Me: I know, but Americans don't seem to use the word 'toilet' and prefer to say bathroom.
Ellie: OK Mummy, I will definitely try to remember to call it a bathroom.

So far so good.

This morning whilst trying my hardest to get both Ellie and Luke to eat up their breakfast so we can get out of the door to school and perhaps not be playing the eternal game of Beat the Clock, Traffic and Red Lights, she shouts her loudest 'I NEED THE TOILET' ever...

Me: Ellie. Please. We've discussed this. We do not shout. We do not call it a toilet. We ask quietly if we can go to the bathroom.
Ellie: At school the teacher says we must ask if we need to 'go potty', but potties are for babies aren't they?
Me: Yes they are but perhaps the other children at school understand that better. At home and when we are out we will say 'bathroom' OK?
Ellie: OK I'll try to remember. But Mummy, there are no Americans here with us at the moment to hear me so it doesn't really matter does it?

I think this could be a long battle.