I wouldn't candyflip if it were my first time doing MDMA or LSD. First time doing each one though? It'll be one overwhelming trip I'd think.
I've candyflipped once so far with 150~mcg LSD and 120mg MDMA. I ingested the LSD first, which was already too much with a sensory overload. After the MDMA post-4 hours on LSD my mind shattered and I had difficulties being lucid. I had a great time once the MDMA settled in though. I sat inside a hotel bathroom with a couple friends who were also candyflipping for the first time. I've never had so much fun before.
I honestly think you should try each drug first. First time LSD/Candyflip during Halloween seems like your asking for a bad trip. Do the MDMA by itself and I guarantee you'll have an amazing time if you have quality, tested gear.