Soak 8 small wooden skewers in water for at least 15 minutes. Heat grill to medium-high. Once it is hot, clean the grill grate with a wire brush. Just before grilling, oil the grill grate.
Fill a large pot with 1 inch of water and fit with a steamer basket. Bring to a simmer. Steam the green beans in the steamer basket until tender, 6 to 8 minutes.
.Meanwhile, mix together the mustard, 1 tablespoon of the oil, and ¼ teaspoon each salt and pepper in a medium bowl. Add the green beans and toss to combine.
Toss the sausage, peaches, and baguette with the remaining 2 tablespoons of oil and 1/4 teaspoon pepper in a large bowl, thread onto the skewers.
Grill the skewers, turning occasionally, until the sausages are heated through and the bread is toasted, 5 to 6 minutes. Serve with the green beans.