My favorite website for quick, easy patterns is Bev's Country Cottage. Many of her patterns are knit on straight needles. Click the links for babies, children, and winter on the top.
I'd suggest knitting tube socks as they'll fit anybody without any heel shaping. Here's a pattern for one that you could do either in the round or on straight needles.
I'm currently trying to get a head start on winter. I'm knitting mittens for children at my local elementary school. The staff tells me kids are coming to the office every day looking for some. To save money, try the one pound skeins of yarn. They go a long way. There's Lion brand Pound of Love and Caron's One Pound Yarn. I get mine from Walmart and Joann Fabrics.
Thanks for doing this!