I need your help...please. I am planning this trip as a surprise for my parents, who are aged 53 and 52 yrs old. They will be leaving from Toronto, Canada and are able to travel for up to six months.

Must see places:
South and Latin America (Brazil, Mexico)
Europe (Italy, France, Spain, Portugal, Germany)
Africa (South Africa, Tanzania, Egypt, Morocco)
Asia (Russia, China, Tajikistan, India, Singapore, Malaysia, South Korea, Japan, U.A.E)
Australia (New Zealand & Australia)

Please let me know your past experiences in terms of booking flights, hotels, etc. They can live pretty cheaply so it shouldn't be more than $100/day per person and they are more into nature than shopping, urban scene, etc.

Thank you very much for your help!