Fill a circle inside the root zone with wood chips, starting 4 inches or so deep and have them get shallower until ending within one inch the trunk. Remember to never pile mulch against a tree trunk as it makes it much easier for disease and insects to get around the natural protection in the roots and then kill the tree. I also dig a very shallow swale (think four inches deep and wide) and use that soil make a very shallow berm that both sets the depth of the wood chips and keeps them in place. If you're not doing huge number of trees it is actually not very laborous to set up and makes maintaining a mulch ring easier in the long run.
Now if your fellow volunteers are so obsessed with weeds, cardboard hidden under the mulch will stop most volunteer plants. You cut through the cardboard to plant into the soil underneath. In this circumstance it works best to start your seeds in pots and then plant out when they get close to nursery size.
Take some time to look at conventional landscaping websites to get an idea of how to arrange plants to please the conventional eye. Usually it's easy to find useful alternatives will fill the same asthetic needs. I make good use of the idea of large drifts and repeated pops of color in my front yard to mix flowers, herbs, perennial vegetables and annual vegetables. If you're dealing with a reluctant audience this is the time to focus on the ornamental functions of the edible plants.
Just some examples, plant roses that produce good edible hips. Talk up the beauty of the flowers and then the color that will carry through fall and into early winter. (Maybe don't mention if you plan to harvest all those pretty hips.) I have very productive chard growing in my flower beds which have a hot pink stem that goes well with the prodominately pink and purple flowers. Rosemary, thyme, and winter savory all provide a dense, aromatic, evergreen ground cover. We have a perennial onion that provides really interesting artichectual flowers in the early spring and then goes dormant as the summer comes in. Echinacea is a mainstay of the conventional flower garden with it's large abundant flowers for most of the year. Artichokes and cardoons have beautiful structure from their leaf shapes and if you don't harvest them they will produce gigantic purple flowers. (If you do harvest, cook the flower stem as well as the bud. I find it just as good as the heart). If you have the resources to build a simple trellis, runner beans can be as ornamental as any vine. They won't set beans if temperatures are over 80 in farenheit, but the flowers are edible and taste like green beans themselves. I have one that's still growing three years on, though we're too hot here for many beans. Many of the herbs have varigated forms with streaks of white, yellow, sometimes even red or purple. I think they taste the same but look more ornamental.
You can probably tell this is a subject that is relevant to my interests. Most of my gardening energy goes to making a front yard that invites my neighbors to come talk about gardening. We've sent many an innocent walker home with bags of herbs that we gathered while giving them a fast tour.
Don't underestimate the value of a lot of flowers and pay attention to when different things bloom. People are a lot more willing to overlook that carrot that's going to seed if it's planted between eight foot tall sunflower bushes and a bed of echinacea. And while they're distracting the conventional eyes, the flowers are providing food for benefical insects and birds that keep pests of your crops.
Yarrow's another great flowering medicinal herb, if you're willing to harvest the flowers frequently, you can keep it in bloom for a very long season. Garden sage blooms with purple spires just a little less showy than those bred purely for show. Chives and garlic chives are alliums with flowers in purple and white. Ornamental sweet potato vines are very popular right now, no reason to tell everyone it's actually the edible variety.
Alright, I'm done for now. There are other things in my yard, but I don't know if they're as likely to be widely appealing as what I've already listed.