Do we get bike in morning after arrival or we need to do online reservations?

We got there at 11am and got 2 bikes with no problem

Depends on the season and how early you arrive.

I called ahead a few hours to reserve as it was peak time and had no problem. There were lots there when we picked ours up around 1130am

I just went in the morning and was able to get a bike after eating breakfast first (appx. 10am).