Rod of Wonder
How about 'no'?
It costs 12,000 gp. How much do I have to split between the two of them?
Plus their father would pitch a major fit if my character gave them something like that.
So craft one. You're a factotum... and
a psion. I assumed the possibility of crafting was a given. Making it a restricted item (if the kids have class levels, they have a class and skills), you'll spend 3,780. You could make one for each of them and have money left over. Yes, you have to be chaotic and didn't mention your alignment, but given that your character willingly steals magic items for the kids, he/she hardly struck me as overly lawful.
Also note the entry on the Rod in the DMG:
The usual effects are shown on the table below, but you may alter any of these as you see fit for your own campaign. Typical powers of the rod include the following.
On paper, the rod can produce any kinds of effects that you want. If 6d6 fireballs are inappropriate for kids then duplicating the effects of Pyrotechnics in the enemy's scrotum surely isn't. Instead of a lightning bolt, manifest a giant rubber mallet that doesn't deal damage but initiates a bullrush attempt on touch attack. Work with your DM. Hell, ask for a discounted price if you two can agree on a list of effects that, say, can't do lethal damage and/or don't offer crowd control stronger than a level 1 spell.
Finally, it becomes the ultimate swiss-army knife of effects. Sure, you might not always get what you want out of it, but the randomization lowers the overall power (less headaches for the DM), and if the goal is to stop them from getting hurt you're almost guaranteed to get something to do that. Further, you don't have to worry about the kids being able to pick the right toy in exactly the right situation all the time. Now it's just "point" and "click", possibly with a command word (I recommend "Kaboom!").