I can't imagine I'm the only Favorite Aunt with LEGO-obsessed nieces and nephews! And who doesn't like playing with their food before eating it?
Look at this fun LEGO mold! If you're willing to risk your kitchen becoming a disaster zone, you could invite your nieces or nephews over for an afternoon to make little edible LEGO armies and edible building structures.
Here's an example of some gummy figures and building blocks you could make with this. I'm thinking a licorice Hogwart's is in order.
The chocolate figures turned out really well here, too. I guess we'd want to attempt making these long before the weather warms up here in Seattle.
Then, later in summer when it got hot, we could use these with brilliantly colored fruit juice to make interesting LEGO shaped ice cubes. I think I'd skip the bricks in this case, and just stick with the mini figures. It would take quite a lot of freezing time, waiting, swapping out the cubes into a freezer bag, and waiting for the next batch to freeze, for these to be impressive. This might be a project I'd do on my own ahead of time and just present the cool ice cubes to the kids when they arrived.
I'd probably stock up on a few different colors of Wilton Candy melts before inviting the kids over for some creative fun in the kitchen.
Here is a helpful YouTube video showing you how to use candy melts with LEGO molds:
Here's another video called Nerdy Nummies:
Hopefully your nieces/nephews parents won't be too mad at you for getting them sugared up since the kids were engaged in an educational (ahem) activity!