Do you think it’s dangerous to let my three year old go sledding with my 10 year old niece? I’m…

Do you think it’s dangerous to let my three year old go sledding with my 10 year old niece? I’m going to be there watching him but being that I’m pregnant I won’t be sledding with him. I want him to get out the house today he says he wants to go play with his friends (he’s in pre school) and I told him there’s no school today and he just seems sad playing alone and my mom said my nieces are going sledding and I should bring him in just worried he’ll get hurt or something