dv-lottery

A consultant told me that you cannot enter the US with a current tourist visa once you have submitted a DS-260 for the DV lottery. I could not find any information about that online. Is what they said true?

How can I remove an accompany from my application? I see a button to add but not to remove. My son is 22 and not eligible to come with us, I don't know why he is in the system. Do I need to contact KCC so they can remove it on their end?