I use the the Jebao DP-4 Autodosing pump, it is only about 75 bucks on Amazon and it works great. You can set it up with 4 solutions, and I believe that it is fairly accurate once you calibrate it. I use it to auto dose PPS pro and excel, it makes my life so much easier.
You will need check valves with this pump, as I have experienced solutions backing down or slowly dripping out of the tubing. I would definitely buy an auto dosing pump instead of multiple lifting pumps with timers. It is a more compact package, it will be easier to setup, it should be more accurate, and if you ever have to change your dosing parameters or schedule it will be much easier.