The fact that you asked the question about yourself without it being chirped at you by the other team tells me you're not a sandbagger.
As somebody else mentioned it could affect your game unless you're also playing on another, more competitive team but that's a decision for you to make. On the other hand playing down could make you a more complete player -- you can work on skills and facets of your game at E level that you'd never attempt in a faster tempo game for fear of creating a breakaway for the other team.
Just wondering -- do you feel like you have to behave more than normal in playing with your dad? Seems like there would be times you'd want to cut loose, either on the ice or off. As great as it is to share the team experience with your dad you might feel the need to play away from him at times.