There are lots of ways of putting candles together, and actually putting so many together just all firing upwards is too far OTT and a bit of a waste of candles.
There must be a way of putting some upwards and some fanned and timing them so that all 500+ stars don't just blend into one torrent.
Look at
http://www.kimbolton.../CH150ZACFL.wmv - OK it's intended to be quiet but for 150 shots there are lots of colours and movement and shape.
There is more to fireworks than what the Yanks call "Skypuke" There really is no need to fill the sky all at once with everything you have. There is artistry in pacing a show with a start a middle and a finale. There was someone on a US forum saying he found the crowd liked the wheels as much as the shells! And a wheel is just some rocket drivers and some colours, -- 30 seconds for the price of two rockets! It's a real cheap interlude.
Research the "musical theatre" and things like the George Mitchell Minstrels, even things like theatre pantomime. There is an opening number with all the performers on stage, then each performer does a number or a sketch then there is the Act-before-Interval, with all on stage. Then the second half is All artistes on for the first number then through some ensembles to the BIG FINALE with everyone coming down the grand staircase to their big bow.
Related back to fireworks shows! An opening number with a big start and some noise then some colours, some movement, some LOUD and some quiet. Cakes, fans, candles, You really can get a decent show for little money!