I would do a spinach salad with poppyseed dressing and fresh strawberries, blueberries, and toasted pecans. I like to cheat and use Briana's Poppyseed Dressing. Everything can be prepped and tossed ahead of time, with the exception of the dressing, which should be added right before serving.
For the main dish, you could do chicken kebabs (see
Wolfgang Puck's Lemon Chicken Thyme Kebabs) and a simple rice pilaf with a bit of grated carrot for colour.
Other, easier and make-ahead options would be things like grilled chicken Caesar wraps,
California Chicken Wraps, or a vegetarian wrap for those who would prefer.
For dessert, you could just set out trays of dainties...mini tarts, lemon squares, brownies, etc., which can be arranged on plates ahead of time. This is what I did when I made a "Canadian" dessert bar for my son's wedding a few years back. It was a bit of work to make a selection of items (even three different things would be great...I think I had seven or eight options for the 100 or so guests), but it is worth it when you can just pull the plastic wrap off the top and sit back to enjoy coffee/tea with your guests.
I recently made a batch of rosemary shortbread, which was easy and turned out really nice. It would be a nice addition to trays. (I think the recipe I used came from the NY Times. I added a bit of lemon zest as well.)
As one more option for dessert, especially if you want to keep it light and simple, may I introduce you to strawberry peach white balsamic vinegar? This stuff is amazing drizzled over fresh fruit like strawberries, blueberries, sliced peaches, etc. You could offer either just a small fruit nappy of fruit with white balsamic vinegar or offer a scoop of vanilla ice cream with fruit/vinegar. I purchase my balsamic online, but you might be able to find it in a specialty store, especially if you have an olive oil shop near you.
These are just some suggestions. Obviously you wouldn't want to pair strawberry spinach salad with Chicken Caesar wraps, giving people salad twice, or serving both strawberry spinach salad AND fresh fruit with balsamic. Hopefully you get some more good suggestions for things that will work for your situation.