Snow Boots - size

Want to get snow boots for the boys. I usually get it in the store, but saw on shoebuy they have a 30 percent off so figured I'd check it out. There's Crocs winter puff boots on there. Anyway have them? Should I go up a size?
My boys are 5 and 3 and they are size 10 and 9. I always hate when they grow out of something so fast. Not complaining they're growing, but I have bought shoes before that they wore once and then felt like the next day they were onto the next size.

Thanks!
Plus with winter boots I know there's a lot of layers.

Snow Boots - size

My sons are in similar sizes and I ordered Kamik boots from Kohls in sizes 12 and 10. They were on sale so I think I paid about $20 for them. They are a little big but, they run on the smaller size and hopefully I will get 2 seasons out of them.

Re: Snow Boots - size

Snow Boots - size

I bought childrens place boots $20. each. Atleast you know the little guy will get to wear both pairs.

Snow Boots - size

I would go up a size. I did on an Lands End pair got 2 seasons.