Looking for some advice on flying a family of 3 from DC to Sydney in December. We have miles scattered across multiple accounts, some of which are difficult to transfer between.

Amex: 330k
Delta: 100k
United: 150k

United seems to have the best availability currently but we are short on miles there. Potentially we could transfer to Royal Orchid Plus and combine amex and united miles. Has anyone had success with this? We're a little overwhelmed with all the possibilities.