You may want to recharge after the 1st light. Based on what you put it, you know how much was consumed.
For the size, it also matters if you want to do 10 flights or 5 flights a day.

My boomerang had 11 servos, most of them digital. I used dual 2400 Nicads. I only recharged after the 5 flight (but measured voltage before every flight).

Good luck,