Hi A.,
I'm not sure about the formula, but as far as the probiotic - I HIGHLY recommend "Pharmax HLC Neonate Powder". You just dip your finger tip in the little bottle and let your baby suck it off your finger.
Bastyr University did a study on probiotics a few years back and found that most probiotic products on store shelves did not contain active cultures, and therefore did not do anything. There were only a small handful that did contain live cultures. I don't know all of the brands, but the one that has always been recommended to me to use by my Naturopath is the HLC brand, being one of the ones that they found the most active cultures. Once you get some, I suggest keeping them in the refrigerator to keep the cultures active.
I get mine directly from my Naturopath's office, but I know you can find it online, including on Amazon.com. I completely understand being budget conscious, but remember that your money is going to better use when you're buying something that you know is working.
I also highly suggest having you and your 17 month old take probiotics. (HLC also makes kids (straws or powder to put in drinks) and adult (capsules) versions.) Probiotics and omegas (Nordic Naturals or Carlson's) are two of the most important supplements to take, especially for growing children.
You can also get probiotics in yogurts and such too (for you and your 17-month old), but make sure that the label says >active cultures<. Some claim to have probiotics, but if they're not active, it's useless.
All the best to you and your family!