Firstly, I'll mention that I'm not an expert on psychoactive drugs and their classifications; this is just based on my understanding of the situation as a chemist.
As far as chemical structures go, Ritalin (methylphenidate) probably should not be considered as an amphetamine:
This comparison (where I've highlighted the amphetamine core in blue) might make it look as if Ritalin is derived from an amphetamine. To a certain extent that is true, but the general class of amphetamines doesn't actually allow arbitrary substitution of the amphetamine core. In particular, the name amphetamine is derived from α-methylphenethylamine, which explicitly specifies the methyl group at the α-position (i.e. next to the $\ce{NH2}$ group). To stick something on the end of that methyl group, as is the case in Ritalin, would invalidate this.*
A more technically correct, and general, term that would encompass both the amphetamines as well as Ritalin would just be something that took away the requirement for the α-methyl group. In other words, we are looking for just phenethylamines.
As for the legal technicalities: I am pretty sure that most phenethylamines are controlled drugs because of their psychoactive properties, and hence are likely to be on the list of banned substances. However, since I did not (and probably won't) read the rules in great detail, I'll avoid asserting that "phenethylamines" could be used as a drop-in replacement in there.
* The table on Wikipedia does actually show one example where the methyl group is modified to an ethyl group. However, I guess that would still be considered a very small change, compared to the piperidine ring in Ritalin.
