A lot of things are said about what is and is not possible regarding dreams about Ahl al-Bayt (A), however, as far as I know, most of them have no basis.

It is possible for the Shaytan to appear as something he is not; in fact, the main feature of Shaytan is deception. 

However, even if you were dreaming about something other than Ahl al-Bayt, there are a lot of things between Ahl al-Bayt and Shaytan that you could have been dreaming about. (Including your own subconscious!)

If, in your dream, the being told you to do something evil or which you know is wrong, it is good to ignore it. It doesn't really  matter where it came from. It could have been Shaytan or something else. 

If it told you to do something good, it is good to accept it.  

If it told you something else, you can also look into it and see if it is a beneficial or destructive thing. 

If it just stood there and didn't do anything, then it doesn't really matter - all you can say is, you don't know. 

So, I don't think you should worry too much about Shaytan being in your dreams. While it is good to be conscious of Shaytan's existence, it is not good to get too paranoid about it (indeed, that could also be a trick of Shaytan!). I think Shaytan is probably busy in other places and maybe doesn't have too much time for dreams unless there is some very specific reason why you think this is the case. 

(This is assuming you actually had a dream about this and are not just asking in general)