I would do it with dwarf hair grass if you were stuck on a grass type. Seems to be more readily available since you will need a TON of whichever you choose. You could also look at Amazon dwarf sword, it looks just like grass.
I used baby tears in my planted amazon tank. Lighting requirements are supposedly quite high but mine grow great under the stock lighting in my 29g biocube. Baby tears isn't a grass type. It's a ground hugging leaf type and one pot split up and plugged can cover quite a large area. Much larger than any grass type.
Hope this helps!