I'd recommend a combo of the two previous responses-pull, vacuum seal in smaller batches(with a smidge of apple juice).
as for how to reheat, that'd depend on all the options you have available. you mention 2 mics only but ask about using an oven. if that is all that is provided/available, are there outlets you can use to plug in your own devices? if not, can you bring your own device?
best options-
if allowed-take a propane turkey fryer/shrimp boiler or two. use them to heat water until almost boiling, then put the vacuum sealed packets in the water to re-heat.
if you must use outlets- use a couple hotplates and stock pots to do an electric version of the above.
options if you have to make do with 2mics and an oven-
1-use multiple pots in the oven and bowls in the mics to heat up the water and packets(another variation of the above preferences)
2-instead of vacuum sealing in small batches, put it all in a large pan and add apple juice(if you used a sauce, you can sub a 50/50 juice/sauce fluid), cover tightly and reheat in oven
if none of the above work for you, this is pretty much all you can do-at least a day before the gig, call in a large chopped/pulled pork order to your local bbq joint. go buy some disposable chafing setups, make sure you have the fuel too. day of the event, pick up your order as close to feeding time as you can while still allowing yourself time to get to the shindig and set everything up in the disposable chafing dishes before the natives get too restless.