Cherry shrimps are likely to be eaten by platys so the Amano shrimp would be a much better idea for a community tank to be honest. I had a selection of Tropical fish and kept Amano shrimp in the tank and they were absolutely fine. They hide for a while when first introduced but once they feel confident with their surroundings they tend to wander all over the tank.
Crabs......not a good idea really as they are known to eat the fish, I know there`s always debate as to whether or not they actually kill the fish or just eat porrly ones but I personally wouldn`t take the risk.
Corys are much happier when kept in slightly larger groups so it would be a good idea to up the number to 6 if you can or look ay pygmy corys instead. With a pair of mollys and platys you`re likely to end up overun with fry, the guppies too so you might want to rethink your stocking ideas? 90L isn`t a lot of room when it comes to fish constantly popping out fry and you could end up with high levels of ammonia to deal with
Neons and cardinals could do with a mature tank and not a recently cycled one so they may be an option for a little way down the line. Rummy`s, harlequins and danios are pretty hardy and entertaining fish but usually need larger than a 90L tank (depending on dimensions) it could be an idea for you to visit your lfs, write down a list of the fish you`d really like and ask here for opinions and advice?
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