The right amount of interiority for secondary characters

I’m working on a sci-fi / time-travel novel. It has two timelines, the origin timeline and a new timeline that branches from the origin timeline’s past at the point where the time travelers reenter their past. Both timelines continue. Originally, the WIP’s scenes were sequenced in logical / causal order, which means the past timeline branch was after some of the future scenes from the origin timeline.

I’m experimenting with starting the novel with the sequence of scenes in which protagonist (from the first part of the origin timeline) shows up in his past (which causes a new, distinct timeline to start). The first few of these scenes are from his mother’s and his father’s perspectives.

I know there’s a risk of annoying readers if I lead them to feel either of these characters is primary in the novel, and then drop or minimize them. (That could have the same sort of bait-and-switch effets as starting in a dream.) I move between the parents’ perspectives as they notice strange differences in their son, and then I have the first scene from the protagonist’s perspective (he is now inhabiting his childhood body).

One of my review group readers advised me to ‘distance the camera’ more from (reduce the interiority of) the mother and father. She suggested showing more than observational hints at their interiority would amount to a promise to readers that those characters were the co-protagonists, a promise I would later break when it becomes clear their son is the protagonist.

I understand my friend’s rationale but it prompts me to question if there are narrative / dramatic situations in a story’s opening in which we can / should give secondary characters more interior depth without making and breaking implied promises that could cause readers to stop reading.

In my WIP’s case, I want the reader to feel the sense of something being amiss in the boy (protagonist). I want to create immediate intrigue as the parents gradually realize he is suddenly very different than he had been. By the time the protagonist’s PoV gets a scene, several scenes in, the readers should have some theories about what’s going on. The protagonist’s actions and thoughts will have planted some clues. When it becomes clear to readers that he is from the future (or possesses knowledge from the future), I want them to (a) feel that revelation was fairly foreshadowed and (b) forgive me the misdirection.

What do you think? If you like novels in which timelines are presented out of conventional order, would my approach cause you to resent being misdirected? In other words, would it be more effective to begin with a scene in the protagonist’s PoV and in which I quickly establish he is a much older version of himself returning (mentally) into his child body? (That is quite hard to do, by the way, and presents its own reader-annoyance challenges.)

Thanks.