I believe at least some of the Ivies no longer require subject tests. Doesn't mean a kid shouldn't take them, but I don't believe they are required, at least not at all. My guess is it would be easy enough to research on the admissions site for each school.
The earlier the better on the SAT in terms of baseball timing. The Ivy timeline appears to be moving up in an effort to keep up with earlier and earlier baseball recruiting and commitment in general.