Set up grill for direct cooking and heat to medium-high. Once hot, clean and lightly oil grates with canola oil. Brush zucchini and squash with 1 tablespoon olive oil. Season with salt and pepper. Grill zucchini, squash, and lemon half, cut sides down, until charred and just tender, 3 to 4 minutes. Transfer to a cutting board; cut zucchini and squash into 2-inch pieces. Squeeze juice from grilled lemon into a bowl. Add lemon zest, jalapeño, honey, and remaining tablespoon olive oil and whisk to combine. Season with salt and pepper. Add zucchini, squash, scallions, and basil and toss to combine.