I'm thinking of buying my 12yo son a cellphone without discussing with his father who is my ex
You really think that's a good idea? Shouldn't the dad have some input?
I think its a great idea!
I don't think you need your ex's opinion on something small like this. If you think your son is too young for a smartphone, maybe a flip phone might be fine.
My son is mature, he knows a lot of stuff, he needs a phone. I'm buying a smart phone.
Well it sounds like you know what to do already, and it would be nice of you to get your child a phone that they really want and need. I'm sure your son will love it.