You are going to get what you pay for in most cases concerning ph meters. The flouro tubes are a very good idea simply because putting up numerous cfls around the sides can be costly and time consuming.
As far as having the flouros on the sides, that is fine, you are right that it might not encourage as much vertical growth but that is not a problem, if anything it will work in your favor and allow you to veg for longer without getting really tall plants.
With 18 seeds, as long as they are relatively fresh, you should be able to get get multiple females. What I would suggest is simple, you should be able to get at least 10 of the 18 seeds to crack the shell, veg them all (you have plenty of light/room) Out of these 10, you should be able to sex them and get at least 5 girls. You could then either throw all but the strongest out and keep her as a mother or just flower 4 of them, have some weed earlier, and keep the one as a potential mother.
This will not only give you some weed earlier, but it will allow you to watch the plants go through the flowering stage and will allow you to better know what to expect when you start flowering your future clones.
Good luck with whatever you decide, you setup seems great.