I have regular trio and 2 yr old boy who uses diapers and I can fit two to three diapers in one pouch. Two other holds my wallet, iPhone, keys (home & car), hand cream, lip balm etc. I'm sure that large one can carry them all too It's not even full. Here's couple pics for you if they help you! We have cup holder in our Bugaboo Bee trolleys for water bottles etc.
I'm not expert with prices but I know that Celine prices are cheaper here in Europe cause it's European brand. Difference can be hundreds depending on what bag you're going to get. I can only recommend DF for you, they're so helpful and their customer service is excellent!
Your trio is gorgeous! I was wondering what colour is it? Also, how tall are you? I'm about 5 ft tall and I am wondering whether to get the regular or the large. Thank you!