Good work, it's quite fun! It reminded me of the struggle of packing the family car when going on holidays as a kid :P The graphics are really cute, and the music/sfx fit well.
As others mentioned, I also ran into the "press space to select/confirm" reflex that ended up sending a near empty rocket to the moon, this could likely be a less obvious key. I also found myself wanting to cancel my selection of an item when I saw it was a bad fit, but it didn't seem possible - albeit that might be part of the intended gameplay, once it's bought, it's bought.