It has nothing to do with how much something costs. As I said before, you can buy something small that actually came from WDW, and have it really be a souvenir. You don't have to pre-order off of Ebay and pass it off as coming from WDW.
A souvenir is something brought back from a trip. It means something thought of you while on vacation. It shouldn't be ordered ahead of time. Then it isn't a souvenir.
It is nice to give people gifts. But to pass them off as being from someplace they are not is just wrong, imho. And saying shh don't tell sure seems to say that is the OP intends to pass them of as being from WDW. How about the OP give them before the trip and say "Here is a little something from me to you"? Then there is no subterfuge, no question of it being a souvenir when it is not.