You have a wonderfully large family, and I am sure you care for them all very well. It is right that as fond as I am of Sirius, I cannot be with him every minute of every day, but in the situations where I need to go somewhere without him, I leave him with a trusted adult friend. He does not seem to mind that. I appreciate your concern over me. It is true that I am young, but boys younger than me have had to take on greater responsibilities in time of need, and so I will do my best for Sirius until we go home or an older member of our family arrives.
Frightened children sometimes lash out with the abilities they have available to them, including magical ones. It isn't their fault. The trouble is that Sirius had been taught that children without magic will hurt him. That they are a danger to him. Please let me be perfectly clear; I am not saying that I believe your Tim will hurt Sirius. Only that if I take Sirius into such a situation, he will think I am deliberately leading him into danger, and I may lose his trust. I cannot risk that.
With respect, if there is no way to arrange this without frightening one of the children, it may not be the best of ideas. I do thank you for your patience in writing to me.