That is incredibly hard. I think no matter what you choose, you will be doing plenty of leg work to advocate for a good fit. Nothing will be perfect. Could you have a full GT assessment done? That might be really helpful in letting you know exactly what you're up against. Have you looked at all your school options? Have you consider homeschooling? Even for a couple of years? Sometimes it helps to think outside the box.
I have a son who is not 2E, but is an active boy. He has an October birthday and went to kindergarten on time (at close to 6). Kindergarten was a fabulous fit socially for him and he had a flexible and accommodating teacher. So he had a reasonably good year. First grade was a nightmere for him though - no flexibility other than a parent volunteer that came every 2 weeks for a pull out. Behavior went down the tubes. So that led to us homeschooling. If I were to go back and try to make it work at school, I would have advocated for the first grade skip. I'm still not sure that would have been enough long term, but I don't regret starting K when I did or having another year at an open ended play based preschool. There were a couple younger, bright kids in K that year that did struggle behaviorally and socially (this was a full day, structured K situation). I know one child really had self esteem and confidence issues after that.
So, I think if your girls could benefit for another year in a smaller classroom with more attention (our preschool teachers were much more flexible than anyone we met at PS), then go with that and deal with the ramifications later. If you have no choice in schools and this school MUST work for you all the way through, then it might be good to jump in sooner rather than later. Half day might be an easier choice than full day?
Good luck with your hard decisions!
