My dad loved to make stuff for my kids (his grandkids). Whether it was adding a lower handle onto the patio door, or building a swing or a sand box in the basement, ... you name it, he loved to do it and they got to see that stuff and knew he made it for them. Now that we no longer have him, I still fondly remember all of his work when I see or think of these things, so I would definitely encourage that.
For Pack racing, unless you are in an ultra-competitive Pack and/or district, I think you would do great overall by letting him build it. Having any track and timer is a HUGE step up from not having one. You do want to model the track slope/height/etc. after the track where you are trying to compete. It it's adult league, well then you need that BestTrack, but if it's not, then follow that one.
I built my first track somewhat following the classic BSA plans, tailored for my Pack's track slope and my basement. The higher quality running surface you use, the longer it will last. Mine was a cheapo with one sheet of $11 smooth paneling from Menards on top, and in the curve, with scrap plywood on the bottom. That lasted for a few years of Pack racing just fine. Eventually we wore out the edges of the material in the joints, but it was great at the time. Couple that with a modern start gate and MicroWizard kit timer and you are in business with not much money spent.