Welcome Steph,
I too have 5 year old son, who is about to finish K in Montessori. We are homeschooling next year. How nice that you got a grade skip and it sounds like the school initialized the move.
I saw your other post about DYS. Go ahead and apply, there is nothing to loose. You can use as many or as few of their services as you wish, the community is great. You get to meet new people in similar situation and hopefully make local contacts, which is truly priceless.
It's nice to be able to refer teachers/administrators to DITD. All of the sudden it's not only you saying that your child is really gifted.