Hi Isra,
I'll try to help.... here are my suggestions.
Your dad (as the principal applicant) must prove his employment/business ties in the UAE with more solid evidence.
Also, as most of your family intends to travel together (your parents and 4 siblings), this may create an impression of wanting to overstay their visit. You and your sister are over the age of 18 years, so this means you are not exactly dependents.
You can also have a look at the Document Checklist for your country of nationality.... and ensure you have submitted all necessary documents and evidence.
For your dad:
Proof of UAE residence permit + copy of valid investor visa (did he also invest in real estate for the investor visa?) + proofs of business (trade license + company bank statements + audit report/balance sheet + any other proofs to show the business is actively trading + his earnings from the business + proofs of his responsibilities in the business + his personal bank account statements + any financial investments)
Also, if he owns property then proofs of it along with the current market value (assessment by a CA)
For your mom
Proof of sponsorship by your dad on the investor visa + marriage certificate + proofs of any financial investments/property, etc jointly/individually owned by her + bank statements.
For your siblings
Proof of sponsorship by your dad on the investor visa + Proof of admission to the school for the current academic year + letter of approval from the school authorities permitting them to take leave from school for XX days + school ID copies + if they have exams shortly after they return
If you don't have an invitation letter from friends/relatives in Canada then your family must show provisional hotel bookings + prepare a day-by-day itinerary showing the places they will visit along with expense estimates.
Also your dad and mom can prepare one explanation.... My Strong Ties to the UAE.... in this make separate sections for property ties + employment/business including current value of it + family ties (brief details of family members who are not accompanying them along with proofs of staying in the same house.... especially if your grandparents are dependent on your parents for financial/well being.... same for you/your sister along with proofs that you/your sister are in college/studying) + financial situation (earnings/investments/rental income, etc)
If your family have visited other countries (which require visas) then each of them can make an explanation: My Travel History (brief details of the visas + entry/exit dates + purpose of visit + copies/scanned visas issued)
Hope this helps
