When I did my Sub-I, the peds director in Austin gave me the BEST advice -
Don't do rotations now that you will do again. Do rotations you will never do again. Now is the time to see things broadly.
That said, I still did mostly peds, I just didn't kill myself with the sub-I's. I did a NICu month (which I guess is really a sub-I, but I didn't know that). I don't know if I would recommend that. I learned a ton and was able to use it in my residency, but you will have 3 NICU rotations, so that may be too much. But I liked it, and I'm glad I did it.
I did peds endo for a whole month, and as such, looked like a freaking superstar around the endocrinologists from day one. Because you will take care of a LOT of diabetes in Peds, and this will help you tremendously.
I don't know how much exposure you will have to the "important" people by doing away rotations in the subspecialties (residents, PD, faculty that will decide your fate.) So don't do an away rotation for that reason. I did an away in Peds ER, which was awesome. I am glad I did it because my program doesn't have a freestanding peds ER, and I learned so much on that rotation. Plus, I got, by far, the best LOR from anyone on that rotation (and who would've known the peds emergency physician would do that? Who knew?)
I also did peds ophtho and ENT (mostly peds - 2 weeks each) and man, am I glad I did. I won't be doing those in residency, but I feel I saw so much, that at least I have a fair idea of what happens to my patients when I send them to those subspecialties.
Good luck!