Not letting our 12yr old have a cell phone

Let me start by saying we have what we call a house phone. It's a good quality cell phone that both (12yr M) (9yr F) our kids both have full access to. They are both allowed to call and text their friends on it. Download approved apps. BUT neither of them want to use it because it's "shared." They will use it if they really need it. Our son especially is feeling left out because all but one of his friends have a cell phone. We were thinking about getting him one for the end of the school year. He's done really well this year and we've seen some great improvements. Here's where I'm a little skeptical.

The friends all talk on snap chat. It's so wild to me that there's so many parents out there that allow their kids to have an app that can't be monitored. Am I just being over protective? He has messenger kids. I've seen some nasty messages from his friends on it. And that's when they no that parents can see the messages. Non of the messages were from him or towards him. Kids making chat groups and bullying other kids. Thankfully our son doesn't contribute to it. It worries me that he could be a target and I wouldn't even no. So my thoughts are... let him have a cell phone and deny him snapchat. Or is there a way of monitoring it without having to check the phone every night?