Hi,
There is a big difference between the two goals you mentioned and the method to achieve them.
If you're looking for brand awareness, you should consider utilizing a method similar to the first option (see more on this below). If you're looking for a return on investment, you should go with the second option (with a few small changes).
The 1st option: the problems with this option are that (1) there are so many fake accounts (meaning you'll be wasting money) + (2) there is a set group of people who go around completing competitions, but they don't really buy anything, just compete + (3) many of the people who participate will not be your target market and (4) you won't get ROI.
The 2nd option: you will have a lower involvement rate, but a better ROI. I would change the prize so that the participant can win another dream vacation for themselves. This is a much better incentive than winning a prize for a friend (at the end of the day, we are all looking out for me...).
I would go with the second option, but make the prize worthwhile, add an option to buy relatively cheap vacations (in order to participate), and have them send in a short 'article' (even half a page) about an attraction/place/restaurant that they loved during one of their previous trips - this would be great to use on your website as it is free content which will improve your SEO in Google (just be sure to get the participants acceptance when they enter the competition).
I've successfully helped over 300 entrepreneurs and would be happy to help you if you need. Just send me some background info by email before, so that the call itself can be 100% dedicated to giving you my advice (maximum value for your money).