Would be the perfect use for them IMO.
A quality Pre Workout has a LOT more than just caffein, However I would never buy/use a commercially branded pre workout, have tried several top brands a while ago and all were rubbish proprietary blends, I would go the caffeine or nothing or a can of red bull or mothers over any of them.
Caffeine doesn't hit me like a good pre workout. I got myself 500g of biocharge from bioflex. So i'll probably be using that to start off with. Only club footy at the moment so i'm prepared to take that risk.
Just double checking that it would be safe to use in an activity like rugby
Creatine and caffeine would be sufficient and be the only supplements whose effects would benefit from the top of my head, as bazza said though, as long as your stores of creatine are topped up it should be fine.
Both these supplements can be obtained from a meat pie and can of coke before the game.