It's a question of hardiness, size and prettiness.
Ghost shrimps and amano shrimp are pretty hardy, but they are colourless (well, amanos have dark red spots down their sides). Ghost shrimp would be OK if you don't mind shrimps it'll be hard to spot. I would not get amanos though. I have 3, a female and 2 male. Yes, they are small when you get them but they grow. The males are about the same size as my endlers, maybe a bit bigger, but the female is the second largest creature in my 125 litre. She's bigger than the honey gouramis, the dwarf chain loaches and about twice the size of the male endlers. The only thing bigger than her is the male cockatoo apisto. Although she's not touched any fish while I've been watching, she is in a tank somewhat larger than yours so they aren't pushed together by lack of space. I wouldn't risk amanos.
Cherry shrimps are hardy and pretty, but small. They grow to about endler size. I've had a few in my 50 litre for 3 weeks. Don't let your boyfriend be put off by the size they are in the shop and they will grow a lot bigger than that. Depending where you go, some cherries are redder than others - like fish, I think they are being bred to intensify colour these days.
Crystal red, crystal black, etc are much less hardy so I would avoid these for your first shrimp.
Don't get any shrimp with long arms. They will grow quite big and eat your endlers. Anything with arms and claws on the end of them will take down small fish. You'll find these shrimp mis-labelled as algae shrimp.
As Colin says, you need decor for them to hide in. I've never fed my amanos, they compete with the fish for their food, even running away with a bit of food in their 'arms'. Admittedly I haven't had the cherry shrimps very long (bought them 23/3/13) but I've had the amanos for ages (bought 18/2/09) - maybe that's why the female is so big. I did lose one of them last year, a female, but the other 3 are still going strong.