teach me about sodium ascorbate

I have noticed on a few posts lately people talking about taking sodium ascorbate instead of Vit C. I am assuming this is because the body absorbs this form better? How do you buy it? How do you take it? Is it something a 3 year old and 5 year old can take daily?? They can't swallow pills so it needs to be powder or be able to be crushed or broken open. DS1 is starting chemo again in a few weeks and my dad was telling me that chewable Vit C is very acidic and will give him cavities (his tooth enamel is almost gone from years of vomiting and the first round of chemo). He really wants to go to school so I want to keep his immunity up as high as I can with the chemo knocking it down.

I bought liquid Vit C from the health food store only to get it home and find that it has a trace of alcohol in it from the extraction process so now I can't give it to the kids. It was the only liquid Vit C I could find in my area.