You would pronounce it like (beh-beh) for bebe. It wouldn't be (bee-bee) because that's not the way you pronounce it.
Bebemos would be (beh-beh-mos), bebo would be (beh-bo)
Lastly, bebes would be (beh-bes)
Bebe is like saying "eh" but with the letter b in front of it, "beh"
Hope this helped :)