What was the biggest/hardest obstacle in your transition from 2 - 3?

We're a maybe three family and as DS2's first bday comes closer, DH and I are trying to have serious talks about permanent family plans!

I don't think we'd "regret" having another, but I'd like to be more aware of what life is like with 3 or more kids!

We're very very lucky to have a lot of family support, a flexible career, and have planned financially to have three kids. So I think I'm trying to emotionally prepare for the possibility more than anything.

The biggest thing is that we both love to travel a few times a year both with our kids and without; and everything just seems made for a family of 4! (Plus leaving two kids vs three kids if we ever travel alone seems like a HUGE difference).

So what is life like with 3 or more? What was the hardest part in expanding your family unit?