Naomi,
I am abit like you, I think I could count on my laft hand the amount of times maddy has used a public toilet & never alone!
Dach, I dont think there is a rule, you do it til your comfortable or your boys start getting severely embarassed!!!

I have the singing in the bath rule still now with Maddy, I pop her & Indah in together, I was Indah & quickly take her out to dryu & dress her & tell Maddy to sing while I am getting Indah dry etc & thenIf she stops singing both DH & I yell "Maddy!" If she doesnt answer we both yell & run toward the bath at the same time!!!
Then we hear a Yeah, I was washing my hair, I couldnt hear you!!! hee hee!