Wow, I struggle with your question because, it’s great to get this type of social event opportunity, but then the what-to-wear for the intended glam , potential need to shop & spend, maybe making poor choices under pressure— kind of gets to me.
So, the pink is not right. The teal maybe, with special footwear & jewelry, because you may not be able to find something on short notice.
I’d actually not focus on length as the best indoor “ elegant”. Meaning, as maybe was your impression, just because a dress is looong doesn’t mean it, or the wearer, will look or feel the most “ elegant. So a gorgeous midi ( I would include cocktail length also for my own environmental norm of gala/ fundraisers, because well, they know not everyone has or is going to go buy a ball gown, and they want to fill tables. But I digress. Just tossing out being open to not- floor- length if a fabulously glam/ elegant but shorter option presented itself. How something looks on YOU is important, not just what’s in a stock photo. Hence since your second dress looks really good, maybe work with that and relax.
Can you borrow or rent? I’d have huge trouble with either, if rental isn’t a real shop, but have to order, try on.
Also, shoes come into play. Sometimes full- length gowns are cut longer than the shoes you might wear, & expectation is that the customer will hem/ get hemmed to fit the footwear. Which takes time and adds $$$$.
OTOH, sometimes long enough for a flat shoe ( dressy) is great for feet, and dancing.