History will forever record Elizabeth Brooks' bat mitzvah as "Mitzvahpalooza."For his daughter's coming-of-age celebration last weekend, multimillionaire Long Island defense contractor David H. Brooks booked two floors of the Rainbow Room, hauled in concert-ready equipment, built a stage, installed special carpeting, outfitted the space with Jumbotrons and arranged command performances by everyone from 50 Cent to Tom Petty to Aerosmith. I hear it was garish display of rock 'n' roll idol worship for which the famously irascible CEO of DHB Industries, a Westbury-based manufacturer of bulletproof vests, sent his company jet to retrieve Aerosmith's Steven Tyler and Joe Perry from their Saturday gig in Pittsburgh.I'm also told that in honor of Aerosmith (and the $2 million fee I hear he paid for their appearance), the 50-year-old Brooks changed from a black-leather, metal-studded suit - accessorized with biker-chic necklace chains and diamonds from Chrome Hearts jewelers - into a hot-pink suede version of the same lovely outfit. The party cost an estimated $10 million, including the price of corporate jets to ferry the performers to and from. Also on the bill were The Eagles' Don Henley and Joe Walsh performing with Fleetwood Mac's Stevie Nicks; DJ AM (Nicole Richie's fiance); rap diva Ciara and, sadly perhaps (except that he received an estimated $250,000 for the job), Kenny G blowing on his soprano sax as more than 300 guests strolled and chatted into their pre-dinner cocktails."Hey, that guy looks like Kenny G," a disbelieving grownup was overheard remarking - though the 150 kids in attendance seemed more impressed by their $1,000 gift bags, complete with digital cameras and the latest video iPod. For his estimated $500,000, I hear that 50 Cent performed only four or five songs - and badly - though he did manage to work in the lyric, "Go shorty, it's your bat miztvah, we gonna party like it's your bat mitzvah."At one point, I'm told, one of Fitty's beefy bodyguards blocked shots of his boss performing and batted down the kids' cameras, shouting "No pictures! No pictures!" - even preventing Brooks' personal videographers and photographers from capturing 50 Cent's bat-miztvah moment."Fitty and his posse smelled like an open bottle of Hennessy," a witness told told me, adding that when the departing rapper prepared to enter his limo in the loading dock, a naked woman was spotted inside. I'm told that Petty's performance - on acoustic guitar - was fabulous, as was the 45-minute set by Perry and Tyler, who was virtuosic on drums when they took the stage at 2:45 a.m. Sunday.Henley, I hear, was grumpy at the realization that he'd agreed to play a kids' party.I'm told that at one point Brooks leapt on the stage with Tyler and Perry, who responded with good grace when their paymaster demanded that his teenage nephew be permitted to sit in on drums. At another point, I'm told, Tyler theatrically wiped sweat off Brooks' forehead - and then dried his hand with a flourish.Yesterday, Brooks disputed many details provided to me by Lowdown spies at the affair and by other informed sources, scrawling on a fax to me: "All dollar figures vastly exaggerated."He added: "This was a private event and we do not wish to comment on details of the party."