If you have Xray copies I'm happy to have a look, but it is not uncommon for these cases to appear. Baby teeth are like a smaller and weaker version of adult teeth, so by the time you find decay, there is often no possibility of just doing a simple filling.
Stainless steel (not silver) crowns are an excellent choice to keep the teeth viable until the time comes for them to naturally fall out and let the adult teeth come through. Some parents want "white" crowns for appearances but these are much more difficult, costly, and poorer success rates. For boys I tell them they have "robot" teeth; for girls they have "sparkly princess" teeth. They won't care unless their parent instills a dislike.
But why does your child have so many cavities? Most likely it is diet-related: sugary drinks and lollies. Discuss possible factors with your dentist.
