For context I have a 1 yr old and an (almost) four year old.

So I realized yesterday that it was the last day to exchange your infant carrier at target for the 20% off a new car seat coupon. My 1 year old desperately needed out of that thing (he is over 26 lbs and his legs were hanging over. It was way to heavy to carry) so I thought the timing was perfect. I would get a car seat that turns into a booster for my older child, and give the baby our old convertible car seat.

Anyway, long story short, we accidentally bought the Graco 3 in 1 Nautilus because we thought it was a car seat/booster. However, it is just a booster (although one with 5 point harness). Would you return it and get something different (like the Graco Milestone) or you think the 5 point harness gives it equal safety/longer lifespan (the box says you can use it starting at 22 lbs so I am assuming it is supposed to be equal to a forward facing seat). The reviews online are great, I just don't want to compromise the safety of my older kid, especially since technically they are supposed to be in a car seat until 4 (no judgement for anyone using a booster before/at 4...in fact I am looking for reassurance from YOU if your kid is in one that it is okay because my husband thinks I am crazy!).