Great advice above.
Keep in mind – The tone of communications is everything. Keep your voice and writing style upbeat and also matter-of-fact. A “nothing personal” approach.
And, don’t take it personally yourself if the other party does get upset. You can be sympathetic “I can imagine these changes are hard” but don’t reflect back any upset feelings. That can be hard, sometimes you have to regulate your own emotions.
If there is a reaction that is in any way hostile, even just snippy, don’t react. Just don’t answer at all. Let it fade into the ether as if it didn’t happen. When you see the person at another time, speak and behave as if the two of you have maintained the best of slightly distant relations. You have the power to make what other people do go away – or at least, you can hold that belief. 
And – all of the above advice is to save you. In the end, we can deliver a message as palatably as possible, but we can’t control how other people react, think, feel, say things. Sometimes maintaining a bit of emotional distance is a good thing.
These situations are tough because we want to be able to do more beyond our current relationships, without hurting feelings, or creating social awkwardness all the way around. But we have to face up to all of that or stay trapped in the same place.