My boys are not very gentle with things; in fact, they are down right rough and careless despite my warnings. I decided to stick to a pocket loupe magnifying glass with a 10x magnification.
The kids are a couple of years older now, and they do like to use the microscope. I know they would really enjoy a pocket microscope to bring on our nature walks. After Laura's question and with Christmas coming I decided to do a little looking.
I suggest getting one with illumination otherwise you will see very little without bright sunlight or someone else holding a flashlight. I was pleasantly surprised to find several models that had up to 100x magnification with very affordable prices. Do they really magnify to 100x though? I am sure the optics are mediocre quality; still, these are something MY three boys will be carrying around in the woods.
I am deciding between the 100x Pocket Microscope from Home Science Tools for $13.95 (top picture) with the detachable (read: prone to be lost) base for viewing slides or the MicroMax 100x from Edmund Scientific for $14.95. I am leaning toward the latter because it is smaller especially for little hands. The slide-viewing attachment is a nice feature, but since we have a microscope we don't really need it.
Edmund Scientific has a variety of models, like a less expensive 30x model and some pen microscopes. Also I found a 30x loupe for $4.70. It has no illumination but it likely has better quality optics, so in the long run it may be the best value. Just don't leave it in the sun...