I think it will be okay. If you think about it, a typical movie scene lasts in between 1-5 minutes, so if you add them all up together (and give each scene around 3 minutes to average it out)...***SPOILERS***
SHELL COTTAGE (Main titles/Intro scene, Ollivander, Griphook, Lupin, Disguises/getting ready for Gringotts) = 15 minutes
GRINGOTTS (Apparating into Diagon Alley, getting past security, mine carts, getting into the vault, finding the cup/Griphook escaping, breaking dragon out) = 18 minutes
HOGSMEADE (flying dragon to the lake, Voldemort discovering Harry knows about Horcruxes, Aberforth saves trio, Dumbledore backstory, Going back to Hogwarts with Neville) = 15 minutes
PRE-BATTLE (Dumbledore's Army, Sacking of Severus Snape, Order of the Phoenix arrives, miscellaneous preparations for the battle) = 12 minutes
BATTLE (Grey Lady, Ron/Hermione in the Chamber of Secrets, Fiendfyre, Fred's death, miscellaneous shots of the battle, vision of Voldemort with Snape, Snape's death) = 21 minutes
IN-BETWEEN BATTLE (Great Hall with all the bodies, Prince's Tale, Harry telling Neville to kill Nagini, Harry's walk to death, Harry uses Resurrection Stone, Voldemort kills Harry, King's Cross with Dumbledore, Back to forest with Death Eaters/Narcissa, Bringing Harry back to Hogwarts, Neville kills Nagini) = 30 minutes
FINAL BATTLE (miscellaneous shots of the battle, Mrs Weasley kills Bellatrix, Harry confronts Voldemort about Elder Wand, Harry kills Voldemort) = 12 minutes
THE END (aftermath of the battle, Epilogue) = 6 minutes
GRAND TOTAL: 129 minutes
Obviously it's not an exact science, but I think it'll all fit in just fine