I wouldn't collect anything for him. The present generation of parents is already on the way to an uncluttered lifestyle and, in view of the amount of clutter we, the next generation above them, have accumulated, quite right, too.
You don't know what he will be interested in later in life, or if he will appreciate it.
However, if you only put a certain amount of money aside every month or so, it's hard to find a scheme which will bring any dividends and it's also not easy to find a system which will allow you to save/invest in your GS's name. (At least, here in Germany that is the situation)
I am seriously considering stuffing a 20 Euro note into a piggy bank every month until the economic situation improves, then investing it in the GS/GD's names at a later date.