C.
A schedule would help him to sleep longer more consistent naps and also help him to eat meals instead of snacking so that he CAN sleep longer naps, and helps to not confuse sleepiness with hunger and vice versa. How often does he eat? At 4 months, I'd guess he eats about every 4 hours. So a schedule would look like maybe:
6am eat
8am-10am nap
10am eat
noon-2 nap
2pm eat
4-6pm nap
6pm eat
8/9pm eat last meal and then to bed
It's important for a baby to nap longer than 30 minutes at a time because less than 30 minutes is enough to trick the body into thinking it had restful sleep, but not long enough to get to the restful sleep cycle. A schedule should help to lengthen those nap times.
I would not start cereal yet, though I'm all for starting cereal closer to 6 months as opposed to 4. The nutrition is in the breastmilk, not the cereal. The purpose of the cereal is to teach them to eat from a spoon...no need to do so quite so soon, and why fill up on filler when they could fill up on the nutrition from breastmilk. That's a primary reason I'm for waiting with cereal until closer to 6 months, among some other reasons.
For pumping, you could then pump at the start of nap time if you were to do the schedule, once he takes to it (could take a week or two for him to take to it if not used to a schedule before he starts waking up on his own around that next time to eat). Or you could pump just after feeding. You likely won't get much in the beginning this way, but it will gradually train your body to make more milk for that feeding. Remember the supply and demand of your body making milk. Your body will make as much as it is used to dispensing. Hope this helps and best wishes to you guys!!