Use only one random generator but make sure it's well seeded. You can place it in the beginning of your main() and either generate sequences of random numbers for use later or make calls to the generator as you go.
Make sure to NOT seed it every time you make a call to it as that's prone to producing same numbers if you are seeding using time to within a second, for example. Seeding your generator only once is a best practice.
In fact, if you are on a Unix-like system, consider making use of /dev/random for your generator. Don't code your own as pretty much any system you use is guaranteed to provide native or have libraries for producing randomness.
In general, consider using generators that make use of external sources (noise from computer hardware) instead of calculating their own.