There are usually multiple strategies to successfully completing a scenario; these can be discussed in the comments below, written down in an additional section of the article or added to an existing subsection.
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.