This was a few years back, and I took notes on flavorings, but not on the gelatin. In line with my usual practices, I think I made this a day ahead and used 1.5 tsp gelatin. It was probably quite soft to work with for frosting/piping, but then adequate the next evening for slicing. I do not remember slicing being any problem with this one. If you decide to go with the lower amount and find it soft, you can always pop it in the fridge for a few hours before frosting and piping with it. If you want to be safe and not have to give it another thought, or if you want to frost, pipe and serve the same day, go with 2 tsp.
Hope you’ll post pics, it sounds like a nice cake!