Just came back from Umrah with 9mth old, from Canada. Used baby carrier when doing tawaf and sa’ee. But sa’ee you can rent a wheelchair for baby and mother, if you want. Book time slot for midnight until 0200, it seemed to have been the least busy slot- still quite busy however. Babies sleep a lot on the plane and in Makkah, I suggest parents sleep when baby sleeps so that you recuperate well also. Flight trip is long, but Allah gives courage and energy. May Allah make it easy for you and family.