The idea for this party takes advantage of the fact that Louis died five days previous to his birthday. These five days can be easily turned into the biggest, best, most luxurious party one can throw.
The theme should reflect Versailles palace. Think gold and silk. As fancy and classy as you can be, and don't worry about going overboard (Louis XIV never did, so why should you?).
Louis displaced the court and required the nobility to live with him at Versailles, and in order to accommodate his court at the palace, modern French cuisine was basically invented. Thus, any party commemorating the life of Louis needs to have haute cuisine. There need to be lots of dishes with sauces. A lot of desserts and delectable treats are also required. Making Marie Antoinette jokes by way of cake is also acceptable.
Putting on a Moliere play would also be wildly appropriate. Louis XIV also enjoyed, and loved to star in, ballets.
Costume dress isn't optional, it's required. Guests can come dressed in period costume, in formal wear, or dressed as their favorite French royalty. Dressing up as ambassadors from foreign courts is also a good option. Peasants should either not be allowed entrance or forced to be the servants for the party. Dressing as clergy is also appropriate, as Louis was a devout catholic. Also: the three musketeers. Heeled shoes are appropriate for women AND men.
There should probably be fountains. For historical accuracy, put them on a timer and have them go off as a sort of show for the party-goers.
Anything related to the musical "Le Roi Soleil" is acceptable for this party, since it is a musical about Louis XIV.
Decorations for the party should follow the elaborate rococo style, or neoclassical French style. Think Baroque.
Above all, be classy.