Car seat advice please?

Does anyone know if the new compact on the go booster seats are any good? I'm due any day and I have 2 bonus kids that are still in booster seats, I was thinking my bonus daughter needed the booster seat with the back on it to position the seatbelt on her better especially since she sleeps a lot in the car and with her size but we looked at Wal-Mart the other day and my husband doesn't think if we got the room for a high back and then we saw them, I just didn't know how safe it was.