Designing multiple buck converters on a PCB
Yes this is possible.  

As well as following schematic design ensure you closely follow recommended PCB layout for the buck converter (e.g putting caps near vin and vout pins of buck, ensuring ground is good etc) as switching regulators are very sensitive to the layout of traces/components.  Often manufacturer will show a reference PCB layout which is well worth copying especially if you are not sure why/how it works.