OTH ... pleased to meet you. Perhaps we can meet up with some current and previous E-Judo/Judo Forum members in Tokyo at this year's Grand Slam/Kano Cup?
In both cases you note ... young bodies need rest. Heck, old bodies need rest. Minds need rest as well. Sleep is my advice.
Other random comments:
Personally, I had experience with a coach ... a former Olympian ... that figured the team should train harder and harder right up to the Olympic trials. Our team was visibly tired at the event and one received a very serious injury that ended his Olympic dream and quite nearly his life.
As you are probably aware ... but because you asked ... the time scales you are talking about are not long enough to make an appreciable improvement in the performance of the athletes. Six weeks out is the shortest realistic time I think. The day before a competition? Not much training at all. Heck, send the older ones out for a sports massage. With Youtube available a team can spend a lot of time in the last week warming up, doing a light practice and then kicking back to watch video of the probable opposing teams and talking about them (and what your team is going to do to them).
Sure, it does happen that someone sees something and then goes out immediately and does it, but that is a rare and unpredictable event, and it comes on top of months and months of conditioning and study. A distraction, you are living in the land that figures that there is no judo problem that 500 more uchikomi won't fix, and you may feel some pressure to take that approach (see NBK's related post). There will be a temptation, because of nerves and because of culture ... especially perhaps the one in which you are immersed, to work "harder and harder" right up to the day of competition. Yes, students should have enough exercise to remain nimble mentally and physically, to reduce stress, to maintain flexibility ... but they are not going to gain anything by being underfed, tired and sore going into a competition.
Another danger besides being burned out, many have observed that serious injuries tend to occur withing a couple weeks of a big event. Just last night one of our students showed up with a jacked elbow ... didn't tap at the MMA gym ... Nationals are in two weeks. Don't know why, but it is often, if it were me I'd add structure to the randori to try to prevent a random knee destruction. Make sure in each case that the uke knows he's supposed to fall down. Stay way from that stupid MMA crap in any case.
On the other end, I shake my head at coaches that give long explanations and hands-on lectures to kids right after they come off the mat. And I saw example after example at last Sunday's tournament. Perhaps they justify it by saying that it is "fresh in the minds" of the coach and the athlete. Really one remembers little walking off the mat, so this is just a headwash for the coach ... sometimes an abusive one at that. Pat them on the back, make sure their owies are iced and wrapped, have a fun celebratory meal with the team .... chankonabe? ... get back to "what happened" another time. Jesus rose from the tomb on the third day ... that's about right for a teen to get back to a normal training routine.
Side note: A serious coach, even sometimes ones who have video as a back up, sits in the chair with a clipboard. He or she records the name of the opponent and key physical fearures ... handedness for example. For both players he records things like attacks per minute and the name of the techniques which are successful or nearly so for both players ... all the measurable features of the match. Things like attacks will allow to feed back important information to the student during the matte ... information that is actually useful ... for example "your opponent hasn't attacked for 30 seconds, make sure you do!" Hayward Nishioka has an excellent clipboard worksheet for the amateur coach, if you buy his book it comes included.