One way to begin is to price each event. How much would you be paid (by a company that pays rather than only reimburses) for each meal, each bar visit, each night/-s in the hotel, and each interaction with staff including but not limited to the front desk in person or via telephone? You will need to discount for bundling and working in one location, but you can get some numbers.
Hotel check-in (or check-out) interaction is somewhat similar in number of details to what other shop type, even if that is unrelated to a hotel? What is the price range for such a shop?
Calling a department is similar in details to what other phone shop? What is the price range for phone call shops?
Your proposed bar visit is similar to which other bar evaluation? What is the price range for something similar?
How many amenities will the shopper evaluate in total?
How much money will the shopper float? Will shoppers demand that any travel costs be advanced or reimbursed?
How much feedback can be encoded in yes/no or multiple choice questions and answers? How much narrative will be needed? Can you produce a survey that is free of repetitions and topics that were not covered in the guidelines? A user friendly survey should bring down the price because shoppers will be pleased with a streamlined instrument.
etc.
Nature does not hurry, yet everything is accomplished. - Lao-Tzu