There are usually multiple strategies to successfully completing a scenario; these can be discussed on the scenario's discussion page or written down in an existing or additional section of this article.
Small coasters will do the trick
First, fix the path system and put maximum research on Roller Coasters only. Do not delete too many of the houses, since that's very expensive.
Now build a small park with compact roller coasters, complemented by some flat rides and shops. As usual, crossing paths, tunnels, and decoration increase the Excitement of your coasters, and since you have plenty of flat land, you should meet the objective easily and in no time.