HI soccermomlynnette,
I (and I think every person on this forum) struggle with this same dilemma, of wanting to take on more contacts than I can afford to support. I have realized that I am only one of many people who are supporting our troops, so I can let a few contacts go by and hope and pray that someone else is helping them out.
The other thing I am doing is writing a LOT more letters, and sending less large packages. I really do love to write letters and send cards, and for someone who isn't getting any support, I figure a letter telling them "thank you" and "I care about you" is worth more than warm socks and beef jerky. (Not that I will stop sending socks and jerky, of course!) So if you do see a contact that you want to reach out to, but can't afford to send a package, I highly recommend writing them a letter. And I'm assuming by your screen name that you have kids, so a letter and/or artwork from your kids is even better!
Otherwise, you are absolutely right in sticking to your 3 contacts and supporting them.
This is my take on it, and it is an evolving process for me. So do what works for you and your family. 