Seamless Family Photo Face-Swap

I have a full family portrait I love—except for the young boy in the green sweatshirt. His expression isn’t quite right, and I’d like to replace just his face with the better version that appears in a second shot of the three boys together... (Budget: $10 - $30 USD, Jobs: Illustrator, Image Analysis, Image Processing, Image Recognition, Photo Editing, Photoshop)