As many other movers before your have found out - usually the hard way - moving and kids don't necessarily go well together. Kids are usually resistant to change, because that means pulling them out of their comfort zones and their friends, inducing a natural reaction of defiance (to various degrees) to the move.
 
One way you can prevent this is by talking to them about the move way in advance. This is so not only can they understand why you're doing all this, but also give them time to prepare for the move. They'll also be able to sort out their feelings better if they know in advance. They can also offer their own inputs and relay to you their own concerns - giving you time to address them properly, instead of just spring the move on them suddenly.
 
Of course, you should also make sure that your kids have the same opportunities they have now at the place you are moving into. If they're a part of the little league, look for the local team and arrange their getting into it. Also make sure that they have a good environment where you're moving to and the schools and neighborhood in general are kid-friendly.