Bad watch, won't watch again, and can't recommend. (Maybe for younger audiences)
I understand that this is supposed to be a "power of imagination" kids story, but there is just a lot of garbage in this.
The kids seem to do some fairly good acting for what they're asked to do, but I'm not sure why George Lopez was cast, but the writing is weak enough that it could easily just be the writing.
The story is designed to look like it's just literally written haphazardly as they go, so it's hard to tell what's badly written, and what's correctly written to make it look like bad kid writing.
While the characters of Sharkboy (especially) and Lavagirl are quite ridiculous, there are some fun things that they include throughout the movie, so its not like the movie is completely without quality, but piled together it was not an experience I'd want to do again.