Dear …
I just wanted to send a quick note to let everyone know that I will be returning to work on __(date)__. This leave of absence has given me the __(healing time/restful period/time with my new baby/etc.)__ that I really needed and I am now ready, able and delighted to be getting back to work.
Thank you all so much for the patience and support you have shown during the time I have been away. I am so happy about reuniting with you all again and getting back into the swing of things at __(name of organization)__. I look forward to seeing all of you again soon.
Sincerely,