Menu carts are on a roll, appealing to millennials’ desire for more choices and visual stimulation, and restaurants beyond Chinatown are jumping on. At Gunshow in Atlanta, Chef Kevin Gillespie wheels out samples of weekly changing items priced a la carte. Diners choose, then he heads to the kitchen to prep the dishes. In January, he rolled out a cocktail cart. At State Bird Provisions in San Francisco, appetizers such as tuna tartare and housemade potato chips go by. Ma Peche in New York City added trolleys for dim sum-style service. And recognizing kids’ picky ways, Allium in Chicago lets youngsters pick from its new Kids Kart Brunch.