If you mean Nam Tok close to Sai Yok in Kanchanaburi province I would rather recommend you to stay in the city of Kanchanaburi and take a one-day trip with the 'Death Railway' to Nam Tok - end station two hours from Kan'buri - and spend some time by the waterfall before returning. To me there is really nothing to see and do in Nam Tok, while in Kanchanaburi you have the Bridge on the River Kwai, the War Cemetary with 7000 headstone for allied soldiers who died during the building the 'Death Railway' for the Japanese in World War II, you may go elephant trekking, and visit the Tiger Temple outside the city, you have the city, the restaurants, etc. - and the local venues within walking distance which I think is a nice thing when travelling with kids.