Who said that there won't be any children in Paradise? Allah (SWT) will reunite the believers with their children in the Paradise (Sura 13, Verse 23 and Sura 40, Verse 8). In the Hadeeth that all children of the believers who die during childhood will be looked after by Sara wife of Ebraheem and will be offered to enter Paradise, they will say: No till our parents enter Paradise. This means that the children of the believers will enter Paradise with their parents.
Wassalam.