For keeping vines alive, pothos can survive a good while in just water. If you want a more complicated live tank, there are instructions in the tanks and vivariums part of the forum. Moss and coconut husk is decent for substrate though. The ABG soil stuff that has charcoal included is probably the best thing for plants and for keeping a terrarium without having to change substrate for years at a time, but what you have is decent. You'll just have to move the plants to clean the tank out occasionally.

I'd argue that plastic plants aren't dangerous unless there are sharp edges or loose pieces. They just need to get cleaned occasionally, but it may be a good idea to remove them just in case.