For that short a vacation, what is the value of your time? Timeshare stays are available on Skyauction and similar sites for about $100/nt with no presentation required. Realistically, that 2 hour presentation will cost you about a half-day of park time, and is that worth the $80 you will save on the accommodation? Note that I say plan a half-day because the presentation starts on THEIR schedule, not yours, and that is 2 hours with the sales person - breakfast before and cash-out time for your gifts after is not included, then you have to travel to the park when the whole thing is over.
Another way to think of it, what is the total cost of your vacation all in with normal accommodation (park tickets, travel, etc). Now divide that by the number of days and if the comp isn't better, it's not worth the time. So say a modest $2000 total for a 4 day vacation, is $500/day, or $250 for that half-day. If the comp is only worth $100, you're losing money.
In general I don't recommend that people attend the presentations unless they really feel that the savings are worth the lost touring time. My last presentation was in Mexico, but for the half-day of our time we got our entire week's SUV rental covered and a free dinner cruise (and the ubiquitous bottle of tequila - surprisingly top shelf brand). To me, that several hundred dollars of comp was worth our time.
ETA: but otherwise, yes, these are legitimate offers, and HGVC is not known for high pressure tactics. The better brands generally have a reputation to uphold. Note that if you are tempted to purchase, DON'T. That timeshare can also be bought on eBay for pennies on the dollar if you really want one; and yes, those deals too are legit. Our total investment for our two timeshare properties was about $12.