It would probably be good to give kids some flavored “Kefir”, which is like a yoghurt smoothie, and commonly available. The reason is that it is loaded with probiotic live-culture bacteria, 10 or more different strains. It is a little sour, but not intolerable, and not as sour as regular yoghurt.
And having a healthy intestinal flora has lots of health advantages, especially in avoiding blooms of antibiotic-resistant bacteria, which can be deadly and are increasingly common. Some doctors are now recommending probiotics in between times of taking antibiotics.
Other things that healthy gut flora do include making food more nutritious and vitamins more available by breaking it down prior to digestion, training the immune system to respond better without overreacting, and regulating the digestive flow.
I got Pelori H which causes stomach ulcers, and yogurt was recommended along with some other foods as a preventative to getting it again.