Background: DP and I live together, with my dd from a previous relationship. We are expecting our first child together in January.
Dp's brother lives in Australia but I'd moving back to UK some time in next 6 months. DP's father works for an airline and can get the family (ie not me and dd) 'cheap' tickets to Oz for about £600 return. DP wants to go with his parents to see his brother in November for 12 days, I would rather DP, dd and I went away together somewhere... DP knows I can't afford full price to Oz (he earns about triple my salary) and says he can't afford to pay for me and dd too. He did say he'd go halves... but I don't even have that if I saved every penny 
it's not that I mind him being away, I just find it unfair that he can jet off wherever he likes and dd and I can't...
For example, this year he has already been to Oz, Hong Kong and Singapore alone on separate trips, together we have been to France, and a weekend in London.
AIBU to think he should think about the whole family and not just himself?