Go to madina khalifa immigration office in the morning, have the form typed (costs 5 Riyals)there and submit along with company NOC and employment verification letter showing your current salary.

Only thing is that since your parents are above 65, you will need to get approval from the captain who sits on the first floor in the same building.

If you already have you wife and kids here, than it should be easy.

Nothing to do with their health at this stage. Once they arrive and if you need to extend their visa, then they will have to go thru medical. For stay of less than a month, no need for medical.

Takes 2-3 days.