Welcome! I enjoyed reading your story. And the end of GT denial is definitely a good thing in terms of finding a good school fit for your son. Good luck! You're in for a wild ride! I think he's definitely past a Ruf left 3 from what you described there. Our kindergarten experience was actually really positive as well. We had a very dynamic teacher who did a lot of personalized and open ended activities. 1st was not so good though. We are homeschooling now. Which is something we never really imagined happening.
One thing I was going to say, is since you have such a crazy GT son, you might consider at some point have your daughter assessed as well. No hurry on that as long as your kids are happy and thriving. I do think it's better to wait until at least 6 if you can?