I am a HUGE proponent of probiotics, but disagree with some points already given. First, I'm a big advocate of raw milk, which in itself is a probiotic, full of life, enzymes, beneficial bacteria and other goodies, if it comes from an unadulterated source.
Next, unless you have a health crisis, probiotic supplements aren't necessary. You can include real food in your diet instead of manufactured supplements: homemade yogurt and kefir, kefir sodas, kombucha sodas and fruit and vegetable ferments. This includes sauerkraut, salsas, garlic, pickles and kimchi. These are so easy to make and SO GOOD FOR YOU. For adults who didn't grow up with these, they can take some adjustment to flavors. But if your kids eat them they will quickly grow to love them. I can't keep my kids off them.
Also, if you're stressed about weaning, why push it? Make it gradual. YOU eat probiotics and they'll start to adjust to the taste and their systems will reap the benefits as they adjust to more solid food.