what are the parameters of your cycled tanks?
I too would recommended using ADA Amazonia but in this situation it won't work for you as leeches ammonia for the first while and will take at least 4-6 weeks or longer to properly cycle.
This is what i would do if someone was to drop 100 shrimps on me and i only have 4 days to set something up to house them from scratch - not saying it would work but ...
Substrate: Ideally Akadama if you can find some. if not get some ADA Africana
Add old sea mud power, bacteria (Mosura Bt-9, Bee Max) and fluvic acid powder (Ebi-ken Sosei) as per many of the set up guides out there to the substrate.
Water: use 100% R/O remineralize with Mosura mineral plus or Bee Shrimp GH+ to get the GH to around 4-5.
The substrate + RO water should get your pH to around 6.0 - 6.8. If you use Africana it should be lower.
Filter: use one of your filter from an existing tank - preferably a canister filter with large capacity of cycled biological media - the bigger the better, turn down the flow if needed. Be sure to put a sponge or some type of prefilter around the intake to prevent it from sucking up your shrimps
Air pump & large air stone(s) - you will need it when the shrimps arrive
Temperature - set your heater to keep it fairly low, ideally around 72 F, make sure it doesn't fluctuate much through the day and night.. and no higher than 76 F. adding cooling if need if it stay higher than that unheated
Dose the bacteria daily per the instructions on the package - believe it is double dosage for BT-9 for new tanks setups.
For plants get a bunch of moss (java, xmas, etc
and a decent light preferably something like LED that doesn't heat up the tank too much. add some ramhorn snails or similar
Test your parameters a day b4 the shrimp arrived and adjust as needed.
Remember to drip acclimatize the shrimps when they arrive and feel them sparsely for the first while until your tank.