Definitely look for something extended rear facing. We have a Klippan Triofix (they are expensive, but there are lots of other more affordable options - there just weren't when we originally bought it years ago). It lasts RF easily til 4. My eldest was in it RF til 4.5, and current 3 year old still has plenty of room. Then it FF as a booster seat up til 12 years, so there really is no way to outgrow it.
If you plan to have more children, a good ERF seat is an investment. With our two, we've gotten nearly 6 years of use out of ours so far, and will get at least 8 years from it before we move to another high back booster.