Jace,
How many days are you going? The amount of clothes depends on the number of days keke.
I would put minimal clothes for me, except for the top. For bottom would wear jeans, which I can wear for 2-3 days. Same for HB. For the kids, 1 pjamas for every 2 days. If you are buying some clothes there, you can reduce the amt of clothes to bring. I never bring towels since the hotel provided, except if my child is still less than 1 year old. I will count the diaper and bring ( if have space), if not buy diapers there.
Adults will use the toiletries from the hotel, with the exception of skin care for me. my kids - I will buy travel size, or if not put in small container, just enough for the travel and throw away after that.
Just for comparison when I went to HK last year.
2 adults, 1 10-yr old and 1 2.5 year old
1. 29" hardcase luggage (1)
2. 1 backpack for baby stuff (diaper, water bottles) - can be hung on the stroller, but if not i'll be carrying that on the plane
3. 1 maclaren stoller.
4. 2 cabin size luggages.
But that because my eldest girl is not using stroller. If I were you hmm I probably would not bring 2 strollers. bring 1 for the bbxun and mini xun will just be carried using ergo. In the plane Mini xun won't have a seat on her own rite, so why you need the maxi cosi car seat? is it for driving when you're in Aussie?