Any bike from Target/Walmart is going to be low quality to begin with.
I wouldn't want to risk getting injured on something from those stores, especially if you are new to it.
I know you don't want to hear "take it back," but maybe you could ebay/craigslist or garage sale it and save money...
Salmon is by far the most widely used fish to make sushi in the United States, and is a very safe bet for an American diet. I would try that for your family.
And best of luck to you! Sushi is not an easy thing to learn how to make. I have failed miserably trying before with my girlfriend.