i need some help

So i’ve been talking to this kid for the past week or so and we both like each other and i think we are going to start talking. The only problem is, he dated one of my best friends back in 7th grade. I know it was only 7th grade and it wasn’t very serious. The majority of my friends say go for it because they want me to be happy but there are a few who aren’t down with it. i’m not sure what do or how to tell her.