My son (5.5 years old) tried this sandals, Jumping Jacks Beach Sport Sandal and KEEN Little Kid (4-8 Years) Newport sandals. He said that these were the most comfortable with both socks on and without socks.
Cons: After having it for about 2 months, it already started to show signs or wear and some tears. I'm not sure if they'll last for another 3 months. For this price, I'd expect higher quality.