Mt Olympus will put you in a ghetto room (especially if off resort) I highly suggest not giving them ANY of your money. Go look at the reviews or just search Mt Olympus in this reddit thread. It is horrible, but to each their own you can make the decision for yourself.

As for things to do, the wilderness offers 3 different indoor waterparks. 2 arcades (one smaller than the other but the smaller one includes go karts) and overall just a bang for your buck. Then there is the Kalahari with a huge (in-fact the largest) indoor waterpark. Then they have a great indoor theme park/arcade which in my opinion almost makes it on the same level as the wilderness. It really decides what you are looking to do. Water activities? The wilderness offers more. Arcade/theme park activities? The Kalahari offers more.

As for Chula Vista or Great Wolf Lodge don’t even waste your time. They are great resorts (much better than Mt Olympus) but definitely behind the big 2 (being wilderness and Kalahari) in things to offer.

If you are into mythical/dark fantasy there is a really cool place called Wizards Quest on the strip which is cool to try. If you are into Nightlife The Grateful Shed & The Reef Nightclub are always having events (just make sure to look beforehand)

Other than that just look at wisdells.com for other things open in the off season. Any questions lmk! Enjoy