Fill up the remaining places on the grass with some flat rides, add benches and litter bins, and build an Information Kiosk. Remove the flowers and unnecessary paths for extra space and money. Also, put research on maximum and tick on Thrill Rides, Gentle Rides and Roller Coasters. Then, fill the beach with some tracked rides and cram as much as possible in there. A Wooden Crazy Rodent Roller Coaster or a Virginia Reel would be a good choice, since both require little space and are relatively cheap to build.
The two rides that must be preserved are incredibly old and thus, prone to breaking down. Ghost Train is 35 years old, with Woodpecker topping an astonishing 68 years. While both attractions suffer from high down-time, Woodpecker is always at risk of a Station Brakes Failure crash in its starting configuration, so setting the ride to run six 3-car trains or one 12-car train as soon as the scenario starts is recommended to remedy this issue.
Once you have repaid your loan and filled up all the space, start expanding your park slowly, building more roller coasters to attract guests. The hills around the park are a good spot to build rides partially underground to increase the excitement rating. It might be necessary to set research to Roller Coasters only for a short period of time. You can also start advertising near the end if you need some more guests.