Testing is expensive and often challenging with a 5 year old. At 5 he also wouldn't be able to do the WISC yet and might hit ceilings with the WPPSI. Testing for 2nd E's at that age is also a challenge since there is wide variation in kids. For example I think it is pretty easy for a dyslexic kid to fall into the "normal" range on most tests that would be used.
For those reasons I'd probably put off testing unless testing is going to open a door or it is needed to change something at school. I'm guessing you don't have a gifted KG program so that mostly rules out the first big reason and the school part is really dependent on the school and what would actually be needed. My 2e DS's accommodations wouldn't have been needed in the type of KG program that he was in at the time but obviously programs and accommodations vary. If it had been less play based and more about sitting at a desk writing it would have been an issue in his case.
As for what is "normal" I'd say it is pretty hard to know when you have one outlier already. I know I was hilariously off on my guess for DD7 because of my experience with DS10. Oddly enough their scores ended up surprisingly similar. My 2e DS is very obvious at both ends of things while my DD appears to be much more even and yet had surprisingly similar highs and lows (but apparently no LD). Even after two full rounds of testing for DS, reading a lot of books and hanging out here for a couple years I completely underestimated DD.
I agree with indigo, keep notes and be alert for issues but I'd probably wait until something makes you "need" testing. If your school is incredibly responsive hopefully that will help buy some time. We got more for DD in grade 1 than we ever got for DS and that was with two full psych ed and 3 years of fighting.
