Heat protectants and straightening

I've managed to go an entire year without using heat, straightening or a relaxer. So now I'm freaking out, because my mom and I are doing a mother-daughter trip to Vegas (it's where she wants to go, don't ask me why, lol) and I want to straighten my hair.

Our trip isn't until the weekend after Labor Day, but Aug. 18 will be my one year anniversary of going natural, so I wanted to do a length check anyway and also trial run this straightening process. I feel like I need to be re-taught all over again, but I'm really leaning towards blow drying my hair and then flat ironing instead of rollersetting in order to get some real measurements on my hair growth. What type of heat protectant should I use and is there a preferred method to do this?

It'll be the first time I'm doing this in a long time, so I don't want my hair to fall out or something, or worse after we come back from Vegas my hair won't curl again. Is this even possible? My mom says the first time water/humidity hits it it'll shrink up again, but I'm really worried about exposing my hair to heat twice within four weeks after a year without it. Please advise....

No that won't happen (hair falling out)

But just want to let you know that natural hair reverts back easily so your hair may not stay straight for very long.

i love IC fantasia hair straightening serum. Its for all heat appliances. It helps my natural hair (transitioning) stay straight for longer
[You must be registered and logged in to see this image.]

I have not used it yet, but I have an event in September that I plan to straighten my hair for. I purchased Nioxin Thermal Bliss Heat Protectant. WestNDBeauty on youtube uses it, and her came out sooo nice after when she flat ironed it.