I also have a 4.5 year old. He'll be starting half day K in the fall and HWT as soon as it arrives. I ordered it tonight. Thanks for the recommendations on that!
He had a psychoeducational evaluation a few months ago and I would recommend getting one. You can get one privately (a post on the region forum might get some suggestions in your area) or you might be able to get at least the tests done through your school distirct as a part of an early K application. We were hesitant at first. There were some moments before the first appointment where we said "Are we really taking our preschooler to a psychologist for educational consulting? When did we become "those" parents.". The results certainly didn't give us all the answers but we learned a lot about our son. Plus, the psychologist strongly recommended early K. We were undecided on that and he convinced us it was a good idea.