How to mix concrete cement
To get air entrained concrete similar to that which you'd get from a ready mix delivery, you'll need to add an air entraining agent to your mix. 

Without getting in to serious mix design, for all practical purposes, a 4:2:1 (stone : sand : cement) mix will likely suffice for a walkway. 

If you're really bothered about cracking, include a layer of smaller gauge reinforcement (eg A142) as an anti-crack mesh.