Hello, Rice milk is a fickle friend, it curdles with other stuff very easily (but less than soya milk). Its not sweet, it is really salty, so kinds love it but its not that great for them because of that. The carton says it should not be used as replacement milk for infants (but not because of the salt, but because it is not very nutritional). We use it as I am allergic to milk and we have it for DD's first drink in the morning so I don't have to go downstairs to get the real milk (rice milk doesn't go off overnight!)...I reckon you could cook with it, but never have, but as you can make porridge with it, I reckon rice pudding would work. Having tried all the alternatives to milk, its definitely the nicest from a taste point of view...and even DH has drunk it from time to time...good luck with it.
I make rice pudding and tapioca with coconut milk - DD thinks its fab.
I don't do white sauces usually. If i use cheese or a white sauce, i take out DD's food first and add the sauce afterwards. She mainly has tomato or veg based sauces. I freeze a big batch and then defrost and stir into her dinner when required.