A. Tonberries aren't stupid enough to fuck with a Tarrasque
B. They'd have to manage to stab it through all that fucking armor plating(their knives are preternaturally sharp, so not too difficult)
C. It would take a lot of Tonberries, and they might wound it badly enough with all the internal organ failure and magical pain-damage to send it back to sleep, but it wouldn't die, in all likelihood. They aren't gods.
On another note, the statline for the average adult tonberry looks something like this:
Strength: 2d20+130
Dexterity: 1d10+15(+35, for females)
Endurance: 1d20+10
Magic: 1d20+20(+40, for males)
Mind: 1d20+10
They're still pretty godsawful tough. Average HP of about, what, ((151*2)+(20*5))*3=1256? Well, I suppose since racial modifiers aren't supposed to count it might be half to a third of that, actualy
Easier to disable them than kill them.
Speaking of which, as Ton(very slowly) grows up, she should get bonuses to her stats. By which I mean like +5 to a stat every two months or so of in-game time, at most. +30 base a year, going from about 90 or so to about 260 or so....so about six years before physical maturity? Ehhhh...maybe a little slower then. +4 would make that take 25% longer, or about seven and a half years....+3 would be 67% longer, or 10 years, +2 would be 150% longer, or 15 years, ending up reaching physical maturity at 19. Which is a little late for how I view Tonberries, so +3 would be more appropriate.
In game time moves uber-slow, though, compared to real world time, so it's not like that'll ever actually get reached. Plus, since she's little, most of the change would be in physical stats for the time beind, and maybe some in mind as she gets smarter(and overall it would be faster, of course, then slow down as she reaches adolescence)
Holy shit I just realized I'm trying to figure out how to stat out how a character would age god I'm a nerd.