What do I still need to do to set up my aquarium?

I was given a 55 gallon bow front aquarium about a year and a half ago, I just finally got it set up (we waited till we were in our house we would live in for awhile) I cleaned and sanitized the rocks (new small pebbles) put the sandstone type thing swim through ornaments in, hooked up the double filter, put in a 14" bubble stone (I am wondering if I ought to buy a second one, my pump is made for two and it looks funny just aerating one side of the tank. The water sat out 24 hours to remove chlorine and I checked the additives on my water from the tap and nothing else was listed as bad in the amounts they had listed on the site. My water temp is 68 degrees, I am not sure what to do about the two heaters that suction to the side, they don't suck anymore. Do I need one, will it be an issue if it gets fully submerged (we have kids so it is likely that the worst could and would happen, My husband is putting straps on it tonight like for dressers to keep them from tipping though it does not wobble. How do I know if the ph and such is right? How do I choose fish, the fish stores around here have sometimes hundreds of breeds and they don't give much info on them. I really love cichlids but my kids love the idea of having a variety so I don't think I can do both if what I was reading was accurate (that cichlids don't get along with much else) I was thinking also maybe gouramis and some other compatible fish. thanks any suggestions would really help! Oh, I have a nitrate testing kit too, do I wait till I have had fish awhile or do it now?