Completing more than one race in a season

For a relative beginner following a stock training plan, a simple, safe, and effective option is to simply take a week after the first race to back away from structured training, then jump back into the same plan part way through so it ends at the second race.  The week after the first race, don't just sit around doing nothing, but don't train by a schedule either.  Do what you feel like, reducing the volume and average intensity.  You likely won't need this so much physically as much as it provides a mental break from the grind of structured training, and recharges you mentally.