Lemo, the Oliva Beach Hotel is a 30 minutes walk at the beach to Flagbeach. You may only surf at Flagbeach and not close to the hotel -> swimmers only.
The Oliva Beach is a hotel outside of Corralejo with no nightlife and you have to take a taxi to the "city" which is not really expensive.
The Oasis Dunas? is in Corralejo and I'm not sure if it is in walking distance because it's more in the middle of the "city".
It depends on you: I prefer the lonelyness in the dunes where no more hotels are allowed to be built and when I want to go to the town, I just use a taxi.
I used to stay in the slightly expensive Riu Palace Tres Islas close to the Oliva Beach.
Hope that helps.
View from top of the Riu Palace Tres Islas (the Oliva Beach is more south and it's a bit more of a walk):