If you're certain that most of the plastic utensils are going to end up tossed, perhaps because no one wants to look cheap enough to ask to have them collected, then biodegradable everything is the best choice, no matter whether you supervise the bacteria or they do their work at the landfill. Either way, you're helping to wean the market off petrochemicals.
One of our readers asked whether, lacking one's own compost heap, "is it better to use biodegradeable or 'compostable' cutlery [table ware] and dispose of it in regular trash, or is it better to use products that are made from a high percentage of recycled materials, but not biodegradable or compostable"? The answer: tableware generally is not made with a high post consumer recycled plastic content because of the difficulty of certifying that the resulting products will be suitable for food contact. The problem comes in if contaminated plastic items make their way into the recycle stream (ever clean a paint brush in a plastic cup?). If you see recycled content advertised for a non-biodegradable tableware line, the feedstock is likely from so-called "post-manufacturing" waste. One alternative is to purchase high quality, durable, non-biodegradable utensils for picnics or barbecues. After the party, collect the utensils to wash for the next party. Not the plates though, as even the best plastic ones will melt in the dishwasher. Under any circumstance, then, "picnic plates" should be biodegradable.