Life just got real

Hey Reddit. About 10 years ago my wife and I bought our home that has an in-law apartment attached to the garage knowing that as our parents age it will be nice to keep them close and safe. My dad who is in his 80's moved in a couple years back has always been a piece of work. Dated women way younger than him (he was 39 when he got my mom pregnant with my brother when she was 17.) divorced for 40+ years. anyways recently we have found him looking at cp on his computer. My wife and I have 2 kids 9m and 12f. Not sure what to do. He has early onset dementia so kicking him out would be essentially elder abuse he would not be able to manage his own life or find housing. We're not sure we want him living on the property anymore with this behavior. Just completely out of loss right now. We're in California. We're going to re-format his computer and put Internet filter restrictions on our router. Any advice would be great.