First, here is everything you need to know about cashing EE bonds:
Second, a lot depends on how the bonds (I’m assuming they are paper bonds) are titled. If only his name and SS number are on them, then HE owes the taxes when they are cashed. (In the “olden” days it was often the purchaser’s SS number that was used, but the bonds were in the name of the child.)
Third, those old EE bonds have not matured yet; they collect interest for 30 years. And you might check before cashing them, because some of the older bonds have a high “base rate” on which variable interest was added over the years. Those are worth holding. You can check the value of the bonds, and their base rates, at the same website I sent you to, above.