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.
At the very start of the scenario, adjust your research funding to maximum and devote your priorities to Shops and Stalls. You need to do this to research the Drinks Stall, which even still will not be researched until near the end of the year. If you have played through Evergreen Gardens, you know what to do next and how to do it: disconnect the unnecessary paths in the outlying areas of the park to keep guests from getting lost. Reduce the inspection times on the two roller coasters to 10 minutes and station a mechanic at the exit of each to prevent Station Brakes Failure crashes, then build some less intense rides. If you are playing through this scenario in RCT Classic, you can make the two coasters safe merely by adding block brakes.
Once you have researched the Drinks Stall, build several of them right away, as your guests will have likely complained about being thirsty by this point. Although much of your real estate is taken up by the two Inverted Roller Coasters, the water and islands should give you plenty of space for more large attractions to help you meet your high guest goal. If you continually expand throughout Years 2 and 3, you should reach your goal with surprising ease. Should you need a boost, whether to get your guest numbers up at the end or to spur revenue growth early in the scenario, you can always advertise.