For a kid's first rod, especially for a trip on which he may be very tough on or break the rod, I'd buy the best telescoping rod I could find (which isn't saying much), cut a piece of PVC pipe as a case and put it inside my suitcase.
I have a grandson the same age and bought him his first rod. We didn't travel anywhere but a 300 yard walk to the creek however. For myself, I have an expensive four piece travel fly rod and some spin pack rods, both telescoping and take down. For all of those, I have made my own travel rod cases from PVC pipe, with plastic press on caps that plumbers use to keep dirt from the end of a pipe till they connect it. The cases are simple, bombproof, custom fitted to the rod with no excess, and incidentally low cost, which is not the main cirteria.
For one spinning rod I like to take north, everything but the first large gathering guide would fit in the light weight thin walled PVC pipe used for built in vacuum systems in houses. The pipe is cheap, strong and light weight, perfect for rod cases. I carved and sanded a wooden mold from a 2x3 board till it was slightly larger and shaped like the rod section at the big guide. Then I heated an eight inch section at one end of the PVC pipe and inserted the wooden stretching mold. It cooled within seconds, shaped to the mold. The finished rod case has a pregnant looking belly section at one end, and the rod sections fit inside beautifully, though I have never found a good fitting cap for the oval end so tape it shut each time with duct tape. I will admit I ruined one piece of pipe before getting the right amount of heat and stretch on the pipe.
For take down rods I wrap a piece of cloth or make cloth sleeves for each section of rod so that they don't jostle against each other when inisde the case and wear away the finish (or worse) when travelling. One of these cases, made to carry the lightest, most reponsive telecoping fly/spin rod I've ever found, has backpacked for nearly 20 years. Wish I could find another telescoping rod like that.
My grandson's first trout, about eight inches long, was more fun for me than catching a big salmon.