That's the thing with anabantids -- they will usually fine at first, but as they grow and establish territory, there can be fierce clashes. Most anabantids are not so much aggressive as they are territorial, but certain species can get ugly.
It appears you've got two paradise fish, two female bettas, and two dwarf gouramis ("powder blue" and "red fire" are just color variations of the dwarf gourami species). It is really tough for me to say which ones would be "safe" to keep. Firstly, we're getting into more subjective territory; secondly, individual fish have different personalities; thirdly, I don't know enough about anabantids to make any recommendation with confidence. With those caveats, my two cents are that I would keep one of the paradise fish and one betta or dwarf gourami. Even then I would keep a close eye on things. This may seem overly cautious (maybe it is), but paradise fish can be nasty AFAIK.
The anabantids aside, there is a lot of potential. If you like long fish, a school of kuhli loaches might appeal to you.
I would also get more of the schooling fish that you already have. The platies were a good choice -- try adding four (or more) of them. Ditto for the zebra danios, but they like more company. A school of 8-10 would make them much happier, and their endless dashing and chasing would probably be fun for the kids to watch.
A school of tetras would be a good addition, but avoid the painted species. They go through a painful process to get that coloration, and this makes them more susceptible to disease. (There's another thing your LFS didn't tell you.) Tetras like the company of their own species, so try not to mix and match.
It might be helpful to look through the
Member's Aquarium Specs board to see what other AC members have put in their 55 gallons. This will give you some idea of compatibility and stocking limits. Keep in mind as you're browsing that planted tanks generally can handle a greater bioload than unplanted tanks.
Edit: Oops, the replies are moving too fast for me. IMO, a ropefish is too much for a 55G, but take that as you will.