We did several moderately long BPing trips in Kelty’s kid carrier, 12-17 years ago.
Consider how the sunshade works (the sun is never overhead in the US, so it needs to have sides to it). A Chrome Dome or just a compact travel umbrella and some velcro straps can do a lot to block sun from one side.
Or plan on a large-brimmed hat on the child. That is warmer and harder to see past, but lighter and better in high winds.
Carrying a little mirror (like on a folding compass or from a make-up kit) is really helpful to check on the kid without disturbing them by taking the carrier off. Eventually, I put a round mirror on a watch band so it would be super-handy on one’s wrist. Or on a wrist sweat band. Worked best for me on the inside of may wrist.
I’d try to discern if you can get the pack bag completely off the frame so you can send it through the wash. Modern laundry detergents are really marvelous at removing all manner of food detritus and bodily fluids. If not, I end up filling a rinsed-out trashcan with warm water and Tide and repeatedly dunking packs with too much kid spit-up, caribou blood, etc on them.