Surely that depends upon your family?
If you want theme parks, you'd probably go to the US. If it's "sand, sea and surf" then places like Thailand, Mexico, Hawaii, or even the Black Sea coast might have their attractions. Or maybe skiing and snowboarding are favored activities, in which case Canada, Switzerland or Chile might have the edge--so to speak. And so on. . .
Of course, your location and budget also have an awful lot to do with what's 'best' for you and your family!