Question: When Frank travels into the future and sees an older Calvin sitting on the floor, Calvin glances up. Did Calvin see Frank?
Question: What are the girls doing when they throw Grace's son onto the kitchen floor? Why are they harassing him, and why is their grandmother enjoying it so much?
Answer: They are blowing a 'raspberry' on his bare belly, just good-natured teasing of a younger sibling.
Answer: It's a vision, not reality, so one could interpret it either way. I think it's more powerful if Calvin is seeing Frank, silently accusing him of being (at least partially) responsible for his (Calvin's) situation.