serious question

so my ex (my son's father) tells me that our son is too old to shower with me. I know he probably shouldn't be but I'm a single mother (I live with my son, have a bf but he doesn't live with us) so when I have to shower I can't watch my son 100 percent and he's only 2 so he's into everything. I've explained to my ex several times that when I do put him in the shower with me I shower while he plays at the other side of the tub with his bath toys and I only do it if I have to when no one is here to help me watch my son. like I said he's 2 and into everything. does anyone else see something wrong with this? keep in mind I do shower after work late at night when I'm able so I don't have to worry about it.. opinions please. if it's a negative one please be nice and respectful about it