If you are not flexible in that you have to fly into Glasgow with only one stop (which I can understand with 2 kids), then Emirates (EK) is your only option, as there aren’t many airlines that service Glascow.
In this case, Qantas point is probably your best bet as they charge less points than EK’s skyward and is much easier to earn Qantas points in Australia. However, please note that Qantas charges fuel surcharges on redemption flight, and it could easily be $600-700 for this redemption. This takes up a great proportion of a discounted economy fare, especially your kids can get kids fare, it may not be wise to redeem economy ticket. So I would advice to aim for business class and above (good luck finding 4 business class seats on EK A380).
If you are looking at upgrades, unfortunately you can’t upgrade on EK flights using QF points so you’d need to focus on EK skyward points. However, I don’t recommend upgrades normally as you usually have to buy the most expensive full flexi ticket to be upgradable. You can easily pay >$3000 for it and no guarantee for upgrade. If you don’t get your upgrade, then you are stuck in a very expensive economy seat.
If you are willing to be a bit more flexible (which is the key to the mileage game), perhaps consider flying into a different city such as Edinburgh, which is serviced by more airlines including Etihad and Qatar. Etihad usually has more seats and very little surcharge. How about a 2 stop itinerary? Consider Singapore airlines’ business class for 68000 points each (Qantas charges 64000 in economy to Glascow), then buy a cheap cross channel ticket with KLM? If you are flexible and are willing to consider these options, then I’ll guide you how to earn points to redeem these.