I would not do the cherry barbs, that'll limit you to the types of fish you can get later. Serpae tetras will perhaps be bullied and nipped at by the barbs. Generally speaking, barbs are not a "peaceful community" type of fish. They are pretty though and moderately active, but steer clear if you want to do tetras and live plants. The barbs may even eat the plants. As far as barbs go, cherries aren't as bad as some of them, but perhaps find another type of fish thats clearly peaceful.
The serpaes will even chase each other around a bit, but they know not to hurt each other.
Regarding your main concern the sediment won't really harm the fish at all.

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