Potty Training Older Possibly Abused Dogs?

I just moved back in with my parents to help them out, but their dogs (a Beagle/Pug mix and a Chihuahua/Pug mix) pee in the house. They were both adopted and we suspect an abusive past. Plus they aren't the sharpest tools in the shed. I potty trained my Dachshund, but he's picking up bad habits from them. I've tried all the methods I used with mine (treats after going outside, going out with them, a schedule, etc.), but it's not taking.

There's someone here with them all day pretty much so it's not like there's no other option. We just put in a new floating wood floor and I'm getting desperate! I'll take any suggestions at all!

By Shara