Benadryl, no. But melatonin, sometimes, yes. My rule is to have a hard cutoff time after which it's better to take melatonin than to continue the cycle of whining, sleep deprivation, and next-day misery. The cutoff is late enough to have plenty of time to try all the other things involving wind-down rituals. It is not an every day thing. I found that having the consistency actually helps establish the rituals too.
Also, bedtime trouble usually means not enough outside time and physical activity during the day. Or that the kids want more of the parent's time.