Legitimate gripe or am I selfish?

My parents have been out of town since last Friday due to my brother being sick and having surgery. Anyway, my mom made it clear she didn't want any of her grandkid at the house because they make messes and they just shouldn't be there while she's away. So anyway I came home yesterday and today for lunch to find my 17yr old and 3yr old nephews there. So between yesterday and today my kitchen seems to be cleaned out. Frozen dinners, snacks, juices, chips. All this stuff I bought for my own kids who haven't really even been home. Every time I turned around the 3yr old was in the cupboards or refrigerator and I know it was him who cleaned out the 8 pack of Ho-Ho's. Their mother, my sister is out of town too and she knows they shouldn't be there. Am I wrong for being mad??? It's not so much the food I'm being petty about but with the way they eat it's like they'll have one ice crea, then another and another..etc....