its probably a bit late now, , you/your son have probably done the job,
but any time i have to either do a job myself or get someone else to do a job that is difficult/expensive and labor intensive, any unknown bits that could fail down the track ..... ie: water pumps, idler/tensioner pulleys/hard to get at hoses (lower radiator hose) that would be a real mongrel or may leave me stranded on the side of the road and not possible to fix without big heaps of hassle ...... i replace them, nothing sux worse than having the unknown or unexpected part fail and be one of those waiting for a tow truck or trying to jerry rig something to get home.
it might cost a few bucks extra at the time, but in the long run
.