I wouldn't mess with the PH. I don't mess with mine whether it is for Domestics or Wilds. I have never had an issue with this. Keep in mind that the PH in the bag when they arrive will not be the same as it was at the sellers. The PH should drop from that due to the waste after 18 to 24 hours in the bag.
I keep a layer of sand in my wild tanks with one exception. I don't have sand in my QT tank. A sandy bottom is what is natural to them and therefore they are more comfortable with it. A thin layer should not make cleaning the tank anymore difficult for you.