First thing you should know is that you need to explain the situation to them. They are old enough to understand things, so I would have a talk with them. Be very careful how you put it up though, as sometimes it could be problematic, i.e. if you are moving due to financial difficulties or any such rather unpleasant reasons.
Next, stay positive about it and never let your uncertainties and fears show in front of them. Moving represents a huge change, but it doesn't necessarily have to be a bad one. Focus on the good aspects, as I am sure there are such. Keep the focus on these and keep reminding your children of them as well. Never make a notion of problems, uncertainties or anything negative about the move.
Visit the new place with them, take them around the new neighbourhood a few times before you actually move. Children usually feel bad about leaving a familiar environment and going to a new one, so it is going to help them if they know where you are moving.
Last, when the time comes, involve them in the process. Have them help with packing or choosing new furniture, design and features of the new home. Seek their feedback when designing their rooms. Things like that will keep them occupied and prevent them from feeling down about leaving familiar things behind.
These are some suggestions I have for moving with children, which I think can help you out. I hope that the reason for the move is a good one and that you can get a new start together with your family!
Pink - my job is actually helping families who relocate internationally. It isn't always easy, especially when older teens have lived overseas for ages and then return to UK. But it is perfectly normal and doable. Lots of preparation, lots of space to express emotions (yes, I will my my friends too. It's Ok to miss them and be sad about saying goodbye) Lots of positive looking towards the new place.
Involve them in the process where you can. If it will mean getting rid of lots of stuff, then make sure they have input into what they will do with their stuff.
Life brings with it change and challenge. That is not a bad thing, it teaches our kids how to approach new situations, cope with change, become more resilient. Thye learn valuable life skills through opportunities like this.