Car seat for big toddler

[love2sleep]

DS1 is 2.5 yrs and quite chunky. I need to get him a new car seat as DS2 will soon grow out of his rear facing seat.

Any recommendations for seats that are broad across the shoulders. I'm dithering about whether to buy one that will just last him until he is 4 or whether to buy one that will last until 11.

thanks

We have Britax Evolva 123 Ultra which has a harness for up to 18kgs then converts to booster with back and can be used until 11ish(supposedly). The width and headrest adjust.