I've shot a lot of weddings, and at every wedding, the bride has a suitcase of products that she lugged to her hotel. These bridal emergency kits should include sets for the bride, bridesmaids, and mothers. An emergency kit should have lots of essentials: spot remover pads, breath mints, hem tape, safety pins, mini sewing kit, bandaids, pain reliever, and anything that would be helpful in a crisis.
I'm not a makeup specialist, but when I started doing photography, I asked one for recommendations. You don't need to use these specific examples and could probably find alternatives, but these are the 5 things I have experience with and always bring to a photo shoot:
Orly "In a Snap!" nail dryer: I can not tell you how many times I've seen bridesmaids, brides, or mother of the bride have to do a last minute touch up the morning of. This is a godsend. It dries in 3 mins and leaves a nice glossy finish. It can also be use for runs in stocking or tulle.
Dior Lip Glow: I carry this everywhere. It's a lip balm that enhances the lips' natural color. The way it works is instead of adding color, it clarifies existing color. It's perfect to freshen up your lips right before portraits, or to keep looking good during the reception. Because it's sheer, you don't need to worry about making yourself look like the joker after you have a few drinks.
NARS Light Reflecting Powder: Fine lines, wrinkles, and pores have to be touched up in editing, but this will ensure when you're taking selfies at the reception, you will look perfect even if I'm not editing the photos.
BITE Whipped Cherry Lip Scrub: This mildly exfoliates and moisturizes your lips. I know this isn't date night, but if you want to have perfect lips, this is the way to go!
Kate Spade Acrylic Straws: These let you stay hydrated without messing up your lipstick. WARNING: never use paper straws! Yes, they are cheaper, but they will disintegrate right in your mouth and drink. It's gross, trust me.
Remember: stay calm, have fun, bring flats for photo ops outdoors (don't want heals stuck in grass), and don't worry about the bottom of your dress getting dirty (it's white & it's gonna happen).