You're not jumping the gun. (From one J to another.)
My son applied ED (even with high financial need), and it indeed was a comfort to my J.
Yeah... If I recall he took one SAT II in his sophomore year (World History)
Then he took:
the PSAT fall of junior year
SAT in May of junior year
AP US Hist. May of junior year
SAT II (Math2) June of junior year
SAT (2nd time) in Oct. of senior year
SAT II (Lit) in Dec. of senior year
Now, he didn't take a lot of AP classes (only 1 junior year and 1 senior year, and he didn't bother with the AP test in senior year because it wouldn't have done him any good at the college he's in), so he wasn't as swamped with tests in the spring of his junior year as many kids are. That helped.
He only needed two SAT IIs for the college to which he applied ED, but tacked that third one on in Dec. of his senior year because one of his top choices in RD wanted that third test. The test date was a couple weeks before he got his ED acceptance, so it was just insurance to take that extra SAT II.
He was, happily, accepted ED to his dream school... but he and I both did a lot of advance planning to make everything time out optimally for him in terms of being properly prepared for the tests, and to be able to keep his grades high and his beloved ECs going full-tilt.
So, you go! Being a good planner helps keep the whole process more relaxed, in my opinion.