I am sorry to know your grandson is so sick. I think sometimes virals can give real tough time.Now what i am concerned is your grandson has pain in the groin and incidentally the testicle are probably in the abdomen or in the inguinal canal
.Sometimes when they are not in the right place we need to get them in the rigfht place by operating on them and i think its high time we attend to this issue.2ndly if he is actually suffering from Hand Foot Mouth disease then i think he is going to have probs while eating because of the blisters in the mouth which can be very painful.What you can try doing is offer him bland food or sweet food or slightly cold
juices .However in the end i would definitly advise you to fix up an appointment with the pediatrician
for assessing him again.