Ocean Sands disco is not open anymore. The Lighthouse disco at Ocean World Cofresi (just past Puerto Plata) is though. Keep in mind that will be a pretty long (and somewhat dangerous) drive back to Cabarete though. THere are sometimes afterhours parties in Cabarete...just ask around as things are winding down...the locals will let you know if anything's happening and where to go.
As far as being a good plan, it should be... but I'd suggest doing Cabarete Sat. night...it's usually better than Friday...and if you want to go to Playa Dorada, do that Friday...
There's no big "night" Thiursday that Im aware of...that's why I suggested Sosua as the two main bars there are almost always crowded and there's an afterhours club within walking distance (AfterOne).