How to keep long hair from tangling

[StillRunningWithScissors]

Hello,

My daughter (8yrs old) has very long hair, which is usually worn in a braid, sometimes a pony tail. She's very active, so this prevents severe tangling (mostly :-)

We are attending a wedding soon, and she'd like to wear it down (I'm taking an elastic band to braid for when she hits the dance floor), and I'm wondering if there is anything I can use on her hair to help keep it from tangling. Leave in conditioner/serum/detangler etc.
Any help greatly appreciated.

A brush. I don't think think anything other than a spray in conditioner and a brush is going to stop hair from tangling. Brush it a few times in the day that's all I can suggest.

If its for a one off then what about straightening it? I find that if I blow dry and straighten then my hair stays quite sleek and tangles less than when it's just in its natural poker straight state.

I have very long hair and keep it tangle free by:
wash
condition
Hair oil
blow dry
a little bit more oil
regular brushing
I use the loreal extraordinary oil, you only need 2 pumps and the bottle lasts for ages.
My hair is just above my bum

Thanks everyone. It is a one off, so I think blow drying and oil are both good approaches. I thought if the hair was coated with something it would be a bit slippery, and not tangle quiet so much.

The hair will be plaited before the dancing starts ;-)

The hair oil doesn't make the hair slippery or oily at all, just smooth, shiny, soft and tangle free