Adoption travel - Options to use OneWorld points for travel
If you start now on a new card you "might" be able to get enough miles to fly UA miles from a chase sapphire preferred/ink plus/bold to do your second trip. Ethiopian airlines availability is usually decent through united, though fills quickly for summer and unfortunately the cost of partner redemption increased recently.
Congratulations on your pending adoption. Be sure to see the destinations threads on Ethiopia, I'm sure there is other airport and Addis info you'll find helpful or interesting in addition to what your agency gives you.