If there is no computers in the other household, I can see why they'd want to stay at yours. I would imagine there's more TV watching too or other tech time. The 5 year old would be like a kid in a candy store with not wanting to leave and the 13 year old with her 'bit" of tech addiction, had to have gotten it at your place?

I would have your husband talk with his ex- about the children's two extremes and see if they cannot hammer out some sort of tech center road so the kids don't get whiplash and socially unbalanced like it appears they are in danger of? All tech is not better than no tech and going from one extreme to the other where they don't understand or have power of choice or any sort of consistency to help them navigate all the new technological marvels (do they have tech/computers in school? Do their friends have computers or technological toys or devices?) does not sound good to me. The parents have to pay attention to the children's reactions; over stimulation without understanding and just going from "addicted" to "nothing" cannot be good?