SO.

DH wants me to engage more with the SDs on household basics.
I think it won't go well, BUT I have strict parameters on what I will and won't do and told him the first time he undermines me I'll be done for good.

My first act was to make sure SD14 (in two days she'll be 14) helped me clean the kitchen up - including sweeping the floor. Then she had to bring ALL the dirty dishes in her room up and wash/put them in the dishwasher. Not a peep of complaint and all was done within 30 minutes. In fact, I defended her with DH when he didn't believe she had done something.
So that went without a hitch...we'll see if it continues.

Tonight I'm going to discuss with both of them about cleaning hair out of shower. The drain screen has been super-glued in (really good this time as it's the FOURTH screen I've put in) and they will get a lecture about cleaning up after a shower (hair also gets flung on the shower walls). I will follow up after they get out of the shower and make sure it's cleaned or they will be immediately cleaning it up no matter what they are doing.
DH won't be home when I do this so even better.