'I'm a electrician by trade so able to do all wiring myself' - OK so we have your capabilities defined, we get to pick up the pieces on lots of systems an 'electrician' has 'designed'
The rest you need to take some time over and properly define the requirement - inc longer term planning for when the kids want there own computer, and keep in mind many kids now use their tablet more than a SKY or other 'TV' device.
If you mix central plus local Sources plus provide local wired and wireless network points in each zone you will have maximum flexibility,
For kids rooms a wired Sonos PLAY:3 or PLAY:5 will sound way better than In-ceiling speakers and offer more flexibility for Line input, wired network connection plus a Vol +, - and Mute button.
In-ceiling also requires you to soundproof the speakers if there are rooms above the speakers.
If you centralise your x2 SKY plus a Freesat box along with a MAC MINI plus run cabling to local Freesat box's you can have max flexibility and cut down on the monthly subscriptions.
Apple TV local to each zone with iPads Airplaying to them is another good option.
Take some time to carefully define the requirement.
A bit of network savvy is also worth considering - managing lots of wired and wireless network devices properly can make a big difference to the performance and reliability of your system.
Yours is quite a typical enquiry we and the installers we work with deal with day to day.
Joe