my little one is only 18 months so i don't know about 2+ years, but i would assume pretty well. the sholder straps are very easy to adjust to get a good fit, just a push of a button. but the recommendation is not to have a winter coat, the slick material can make the sholder straps slide and the puffy nature of coats gives a false sense of snugness with the straps.
As the coldest part of winter approaches, parents everywhere bring out their babies' winter coats or snowsuits to keep baby warm during travel. However, thick winter coats or snowsuits can compromise your child's car seat safety. In order for a baby car seat or toddler booster seat to function properly, the straps need to remain tight against the child's chest. Winter coats and snowsuits make car seat safety difficult because they change the way a child fits into the car seat. When the car seat straps don't fit the child properly, there is a chance the child could be ejected from the car seat.
My daughter is 13 months and I don't believe that this seat would fit any better/worse when a child has a heavy coat on. I typically put her in a lighter fleece jacket and a blanket over top if it's really cold (I live in PA). I do believe the recommendation is to avoid heavy coats in a 5 point harness due to the nature of the coat causing the harness not to fit snugly against the chest. I'm sure you'll find it just as hard in any other seat.
Unfortunately, I can't really answer this question. Our daughter is only a year old, and she fits fine, even with a coat. Usually, we put her in the seat in clothes and then, if it's cold, put a blanket over her. Also, you can loosen the straps. But I just don't know how it would go on a larger child. Good luck!
As it is recommended to remove any jacket, I do believe your child would fit. The straps adjust very easy so even if you need to adjust them it takes seconds. But my daughter is just 9 months. So I cant be 100% sure.
Coats should never be worn with ANY car seat. Fluffy winter coats will compress in a wreck and make the harness too loose to provide adequate protection for the child. Try putting the child in the seat and tightening the harness appropriately, then have the child put the coat on backwards AFTER buckling. This way they get to stay warm, but their safety isn't compromised. Look up car seat safety recommendations for info on correct harness tightening.