I have been apprehensive about bathing both of the offspring simultaneously, because of the juggling of slippery wet bodies, and because both of them are remorseless bathtub urinators, and they could easily create a sort of bathtub pee soup between the two of them that would not brighten any one's day. And by any one's, I mean mine. Max, however, forced my hand by requesting Maggie's presence in the bath with him on several occasions. Apparently, he is bored of his other bath toys.
It actually wasn't as difficult/gross to duo-bathe as I had feared. Maggie did pee (twice!), but it was at the very end of the watery jubilee, and it was mostly contained in her baby bath. No one slipped soapily out of my grasp and down the drain, and everyone got more or less clean, and so I declare myself Mama Bather Extraordinaire. I will be wearing a crown from now on.
Max LOVED having Maggie in the bath with him. He "helped" wash her, getting entirely overenthusiastic about the soap and the washcloth. He considered letting her play with his alphabet letters, but decided that they were too precious a resource to share. He let her look at them once or twice.
I know that Maggie looks worried/disgruntled in all of these pictures, but she was actually quite delighted by the bath. She enjoys baths, she enjoys watching Max, and she finds the stripy shower curtain compelling, and so the combo was a smorgasbord of sensory delights. She kicked her feet and cackled wildly throughout most of her scrub-down. In the pictures, cackling and kicking seem to translate into worried/disgruntled, so you will have to take my word for it.