I am thinking of places for our upcoming holiday. I have a 7yr, a 3 rd old and a 1 yr old. Together with my parents as well. Where would be a great all-rounded place to visit?

I second Taiwan. There's bustling Taipei with its night markets, soak in the hot springs in Xin Bei Tou or you could head down to Tainan or Taichung where the famous Sun Moon Lake is. Japan is good as well. There are a lot of shrines which your parents might like to visit. There's Disneyland for the kids and a park with deers in Osaka.