Is there such a thing as "food grade CO2"?
According to The Brewing Network, industrial and food grade CO2 generally come from the same plants:


  The slight difference between industrial-grade CO2 and food-grade CO2 is the type of tests that are done to qualify CO2 as beverage or beer gas-grade compared to industrial-grade. Currently, the FDA's requirement for food-grade CO2 a 99.90% purity rating. The other .09% is made up of impurities such as hydrocarbons or nitrogen. Industrial grade CO2 is 99% pure CO2, also containing impurities such as hydrocarbons or nitrogen.


However, the nature of those impurities extremely important.  They go on to suggest:


  One impurity that all homebrewers should be aware of is benzene. Benzene is a no-no for homebrewers. If the CO2 that you are purchasing has high benzene levels, it will leave you and fellow drinkers with terrible headaches. When I say high levels, we are not talking about much. Benzene is usually an impurity that is referred to in PPB. The benzene level should be around 20 PPB.


They suggest you ask for a profile of the impurities, although I suspect that Dick's will be unable to comply.   You will have to assess your own tolerance for risk, but you may better off seeking a more appropriate local vendor.