I have both cameras the 7Dii and the 5Diii, the 5D will give you better resolution with those lenses you have and less noise at higher ISOs. I love mine. With the rebates and price of the 5Diii I have seen at Camera Land, it is fantastic. That being said, if you are disappointed with the resolution of the 7Dii, it is a tough call. Me personally I saw a difference and went with a new body.

Great photography is not about being in the right place at the right time, it is about putting yourself in the right place at the right time.