If the Jv program idea is to be the learning ground for varsity then a few short term goals would be nice as well.
I implemented a measuring device a few years ago that my kids still compete in. See how many players can juggle a ball allowing it to bounce on the ground once and touch it up once about chest high. We have a player did 1001 and ended with a shot on goal. My Jv girls have tried to knock her record off, closest so far is 400. Counting out loud adds pressure and competition.
I also use a GPS and record distance and top speed they love setting the record on that. Plus I show them the area that they cover in a game and it always amazes them.
Like many have said before work on making them a team. There will be, just by the way things are, forces that will pull at them. Removing the stigma of JV for them as well as making sure you (I) don't say things even in jest that are not 100% positive and constructive.