I think you are on the right track. Most cleaning companies do a thorough job, but you will run into some stinkers. Interview several people and read reviews of the work online. I am not a fan of big commercial cleaning companies. Some hire just about anyone to do the work. They usually don't pay decent wages so some employees just wont be motivated to do a wonderful job. I am a one person cleaning business and I like it that way because I CAN guarantee my work. Not saying ALL companies hire bad people but some do! I hear this from many customers who hired me because I do all the work.
Dealing with allergies is tough. I also happen to be an RN, and can tell you that most likely, even if you DO hire a cleaning person, you will also have to do touch ups in between. Dust is all around us. I don't know if you know this, but we make our own dust! Plus any pets do as well. Older homes tend to have more dust. You cannot get rid of it but you can control it.