This is a great question, one that highlights the difficulties in measuring the environmental impact of different activities and materials. I will rely on a few web resources I have seen in researching this material; I will give the website urls so you can look at them also.

First, when choosing to use synthetic materials in building a restaurant, there are many things to consider. One good thing to think about is the impact of the materials used initially in putting up the restaurant vs. the impacts of other practices in this business, like exclusively using locally produced organic food for as much of the product as possible. In the long term, this sort of thing could far outweigh any benefit of exclusively using "green" building materials. The use of energy and water saving appliances in a business like a restaurant could also have a huge impact in the long term. Also, synthetic materials can be chosen wisely, for example the use of PVC is, in my opinion, never justified (see http://www.healthybuilding.net/pvc/ThorntonPVCSummary.html). In using renewable materials, one must also think about whether or not those materials have genuinely come from a sustainable industry. Many wood products for example come at the cost of tropical rainforests or are shipped great distances. How much energy does that use, and how much Carbon dioxide is produced in the process? Using third-party certified wood products is definitely preferable if not a requirement for green building.

Non renewable resources can be environmentally friendly in the long run, if you consider the long list of things that should count when planning a construction project (see http://www.buildinggreen.com/auth/article.cfm?fileName=090101a):

Whenever possible, building materials (even renewable resources like wood products) should come from reclaimed/recycled/salvaged/agricultural waste sources. Products that reduce material use (ie. are made with less mass of matter then other similar materials but that still perform equally well), those that require little maintenance or are rapidly renewable are best.

Materials that contribute to a healthy environment are also important - materials that give off toxins or pollutants should obviously be avoided, and those that prevent the spread of or remove contaminants, or those that improve light quality, reduce noise or reduce the amount of energy required for heating are good environmental choices, that I think could be justified for use in this setting even if they are synthetic. The task is to do your research and find out what synthetic materials are being developed that meet these criteria.

As far as the use of paper towels vs. hand dryers is concerned, everything I have read suggests that dryers are best, as long as they are the newer high efficiency ones that use little energy and are actually effective. Most of the problem with using dryers is that generally they do not get hands completely dry, and wet hands spread bacteria and viruses. Paper towels are efficient at drying hands and removing bacteria, but of course are more expensive in the long run, take up landfill space and result in the cutting down of more trees. Choosing a high efficiency hand dryer is good because it works to dry hands (mostly by blowing the majority of the water off and leaving just a thin layer that evaporates quickly) and also it turns off automatically, so does not waste energy.