Just my 5 cents, dont worry about floating point math, while you are about to design a game.
I would like to see that the developers here are more focused at game play quality than speed.
Develop the game, make it fun! Then if you find it running to slow, optimize the inner loops and the most critical sections.
I have developed two games, maybe not the most graphical intesiv (no 3D), both uses floating points in their inner loops, and I have at least 30 fps on the slowest devices.
I think fun is more important than speed.