Hi Welcome to Fish Lore

It sounds like you've done some good research before jumping in. Good for you! Many of us didn't.
If you're planning to use Tetra Safe Start, you should add a couple of fish at the same time. They'll provide the
ammonia that the bacteria in TSS needs to continue to develop.
Make sure you follow the directions on the bottle. I don't think you're supposed to do anything for 10 days after adding it and the fish.
Guppies are fun and very pretty. Have you looked into Glo-Fish? They're very colorful. Perhaps a mixture of Glo-Fish and Zebra Danios? They look like a different species, but are really the same. The Glo-Fish are genetically altered.
Cray fish wouldn't be a good choice with fish because, well, they eat fish.

Shrimp are fun. Maybe try some Ghost shrimp. Several members have Cherry Shrimp, I've never kept them so I can't say it they'd be compatible.
Good luck and have fun with your tank.
We'd love to see some pics when you get it up and running.
