Any special places we can go this october where my kids can have fun in Harbin?

Well, it rarely snows in October. So you may take your kids to indoor skating and skiing resorts. For example, you can go to Xinxiu Skating Club at No. 22, Baqu Street, Daowai District. If you want to see a city of ice and snow, you may postpone your visit to January or Feburary. :)

thanks Lucy! any suggestions for ski resorts? or any resort that has snow boarding or i guess the tube that goes down a slope would be fun.

Most ski resorts are open from late November to late March. So I am afraid that they will not be open during your visit. As I know, the Wanda Indoor Ski Resort is under construction. It is located at the crossroad of Shimao Avenue and Hongyuan Road, Songbei District, and is predicted to open in July, 2017.
You are advised to keep close attention to the news before going there.