The theme in your question appears to be how to derive the answers that they want to see rather than answers that you would be capable of providing yourself.
For question 8.4...
Based upon what you wrote, you are leading a group of 4 other family members, including 3 children, on a trip to the UK. It's reasonable to expect that you would have spent some time plotting out an itinerary and have some very specific things in mind because the head-of-household would do things like that. It is natural that you would want to assure the visit was meaningful for your family while simultaneously accounting for their safety and well-being. You can take that itinerary and write it down (using separate sheets if need be). If you haven't given lots of thought to it, then it would be a good idea to do so before your next application. The answer to question 8.4 isn't meant for you to guess what they want to see, it's to put down the plans you have made.
For question 5.19...
This is a natural extension of the itinerary you contemplate. You would compute this figure by adding transportation, lodging, meals, entertainment, and souvenirs for 5 people. There is no figure that they want to see, instead they need to see the figure that makes sense and is consistent with your plans. If the figure is out-of-whack with your lifestyle or financial capacity, they will assume that you are misrepresenting the purpose of your visit and refuse. Also, if the figure does not dovetail with your itinerary, they will assume that you have some other purpose motivating your application and refuse.
From your other question, I'm given to understand that you want to take a family of 5 from Saudi Arabia to London for 3 days and then another 3 days in Manchester and then to return to Saudi Arabia. And you are setting aside £10,000? All that money for 6 days? At what proportion of your income? Why so short a time? The children will be exhausted! Including 13 hours in the air flight time. The ECO is likely to see it as out-of-whack and you should spend some time thinking if further explanation is needed.
For your other question about accommodation...
You can write down the required information in question 8.10. Since uncles are not part of qualifying family, you would need to explain why they are willing to do this for you. Do they always do it for their nephews? Have they done it before for other nephews etc?
Overall, the answers should reflect what you have figured out and not what they want to see. If you focus too much on what they want to see, your application will become inconsistent. If the application is inconsistent or out-of-whack, they will dig down and find a reason to refuse.