it depends how you react to it normally. some people will pass out and be groggy in the morning, some can stay awake through it. melatonin doesn't do much for me, but benedryl will knock me on my ass in 20 minutes.
Melatonin is only going to help if you are taking it at the same time everyday for a while and even then the evidence is sketchy. The point of it is to reset your circadian rhythme, it doesn't really "make" you tired. Try ambien if you can get some. Worked excellent for me last year, only use it when you need it or you can become dependant though. Also it helps you fall asleep, but typically only lasts 4 hours and might not keep you asleep. It is among the few sleep aids that give you true restful sleep. Benadryl (diphenhydramine) will make you tired, but can last into the next day and gives you more of a drunk sleep. Not all that restorative. If you are like me it lasts well into the next day.
Here are keys that work for me, though it depends what you want out of Coachella. I like to go hard all day and then actually rest at night. Until the last night and then we go all night. Coachella is a marathon and if you go huge the first night you will probably be worthless the next morning. I am not going to say partying hard all night will wreck your weekend, you'll have fun, but if you are there for more than that and trying to cram all you can in then take it easy the 1st few nights. Maybe a beer or 2 back at the campsite to recap the day and then hit it because that sun is sure as hell not going to let you sleep well past ~10 AM.
Having a shady set up to reduce heat. EARPLUGS and although it sounds stupid an eyemask helps alot. Again I am assuming you are camping. I slept like a champ last year while a couple in our group where definitely haggerd some of the time due mostly to not resting right. It's a tricky balance, this is what works for me. Goodluck.