When making rice for a large group, you should take a hint from the restaurants and do it in the oven in a large roaster or baking pan.
Put the rice in a pan, add boiling water and salt, and then cover with foil.
Or you can make it like a very large pilaf which will make it more special.
But oven in large pan is the way to go and make it fresh.
I don't have amounts because you will know how much you need to make.
Common knowledge is 2 times as much water as the rice, and common knowledge is, generally, too much water, particularly in large batches.
Again, a restaurant recipe will do you well.
cooking.stackexchange.com/users/3479/Doug Johnson-Cookloose
You have to be very careful when preparing rice for consumption later.
Cooked rice can contain a toxic spore which causes severe food poisoning.
You should cool the rice as rapidly as possible to prevent too much of the toxin being produced by the spore.
cooking.stackexchange.com/users/4194/ElendilTheTall
ok, so this may not be a correct answer for a cooking site, but... maybe you could buy enough cooked rice on the day of your event from a local chinese restaurant? : )
one less thing for you to worry about on the day of your big party (and nobody needs to know)!
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Rice will dehydrate when it's left over night.
So it will be very dry when you try and reheat it.
Cook it ahead of time, but keep it as close to ahead of time as possible.
The less time it sits around, the better.
When it's time to serve, place a little water in with the rice, cover it (slightly vented), and then microwave till warm.
The steam from the water will help rehydrate.
I don't think the result is quite as good as fresh rice, but it's much easier.
cooking.stackexchange.com/users/1259/yossarian
I have two options here..
one was not easy and the other one was rather creative (but traditional) Fried Rice.
A quick way of reheating a large amount of rice from the fridge (I guess you pre-cook all the rice prior) is to make fried rice.
Just heat up a wok and add a bit of oil will do the job.
It may take you a few rounds, but it's better than reheating rice in microwave.
Make Rice dumplings - you may have heard of Chinese rice dumpling which is usually made of glutinous rice, but you can use short grain rice instead which is sticky enough.
It may look kinda fancy if you serve people with rice dumplings.
The advantage of rice dumpling is you can keep them in hot water before you serve and you don't need rice cooker as the whole cooking process is in a pot.
I cannot find you the exact recipe, but this blog article seems pretty good.
http://eatfirstthinklater.blogspot.com/2006/05/making-chinese-rice-dumpling-bak-chang.html Just ignore all the ingredient and put in rice only.
I got some links here: http://en.wikipedia.org/wiki/Zongzi
cooking.stackexchange.com/users/2951/Foodrules 
I do this for parties all the time.
I put several large spoonfuls in a plastic ziplock bag.
Seal the bag, stick it in the microwave for 3min intervals till it is hot enough.
flipping the contents around in between heating.
cooking.stackexchange.com/users/62549/Carl
I am having a party. I have no rice cooker.  I plan on cooking the rice the day before.  Is it possible to reheat it and have it taste good?  How to?
Reheating rice for 25 guests
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<rice><bulk-cooking>
cooking.stackexchange.com/questions/10959
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Cooked rice can cause severe food poisoning, but if you are careful and cook it close to the time of consumption it should be fine to microwave it with a little added water. If short of time, a local Chinese restaurant may be able to deliver enough cooked rice at the right time. Put a little water in with the rice and microwave until warm. Alternatively, you can get large amounts of rice from a local Chinese restaurant.
Rice can cause food poisoning if not cooled and reheated properly. Try buying the rice already warm from a local Chinese restaurant. Put a little water in with the rice and microwave until warm.