I've been an educator for quite a while. In that capacity, I made it a rule not to touch a student except when I was coaching. In the area of coaching, it was often necessary to physically guide students to certain areas of the court and move athletes' hands to help position them for appropriate ball handling. A genuine pat on the back is also an incredible motivator!
In aikido, an instructor is very much a coach. It would be a disservice to the students not to make appropriate contact with them. In the information given to parents, make it clear that there will be appropriate physical contact. Also, make it very clear that parents are always welcome to view sessions (as a matter of fact, it might be good to make it mandatory so that the dojo doesn't become a daycare!).
Or I'm completely wrong