Fit on Sunday Brunch

I'm hoping someone can provide some input on how the Sunday Brunch Jacket fits compared to other O+S patterns. I've put together the front and back yokes and front and back panels in a 2T (plus 1" of added length in torso and sleeves) so far and it's looking pretty small. My daughter is 21 months old; other than her height, her measurements align with the 18-24 month size so I was hoping this would be slightly roomy and at least last the spring and summer. I'm specifically worried about shoulder room. When I place the jacket in its current state on her, the edges of the yokes come to the edges of her shoulders so I'm worried about how it will fit once seam allowances are used up. To give context, her 2T Rainy Days Jacket is pretty roomy but it doesn't close particularly well with something like a thick sweater under it (though it's lined with fleece so I'm sure that's part of the issue). Her 2T Class Picnic Blouses fit in the shoulders and are roomy elsewhere. Her 18-24 mo. Book Report Dress is tight but she can still squeeze into it. I guess my question is if I should keep forging ahead with the 2T or if I should re-trace the pattern and scrap what I've done so far. Any thoughts?