It looks like most of us are in agreement on this one.
I would have been happy to let the guys go with a warning, until they pretty much condemned themselves. After that, I felt like I had to deal with it.
Since I knew Van was downstairs, getting in some piano practice, we went to Parker and Van's room. I thought about things on the way downstairs. Once we were in the bedroom, I gave Paden one chance to back out. Whether he stayed because he knew he'd screwed up, because he thought his dad would be harder on him than I would be, or because he was afraid of being banned from tonight's sleepover, I don't know. However, I felt sure he knew he'd broken some rules, so I wasn't worried about being unfair to him.
I lectured them mildly while baring them both. Both of them were in boxers (darn it!), but Paden is a bit older and bigger than Parker. I'm pretty sure he's not 12 yet (I have enough trouble keeping up with my kids' birthdays), but he is showing the first, early signs of adolescence, which was pretty cute.
When both boys were bare, and I was sure we were on the same page about why they were in trouble, I had Parker fetch the spoon, while I put Paden over my lap. I took the spoon from Parker, but tucked it under my leg, instead of using it.
Paden got enough of a hand spanking to push him past broken sobs to real crying, but I kept it on his bottom, and stopped when he started to really cry. Then I fetched the spoon. I addressed Parker, since I wasn't sure Paden would be able to understand me, and explained that the finish was because they'd not just broken a rule by sneaking into Tracy and Charlie's room, but they'd done it to break another rule (snatching extra screen time). With that, Paden got about 12 swats with the spoon - mostly on his bottom, but the last two on the sit spots.
I rolled Paden up for a quick cuddle, then helped him to his feet, and it was Parker's turn.
Parker got almost the same thing that Paden had, except Parker got a few extra with the spoon. I feel that my boys should know the rules better, and so consider them more complicit when something like this happens. This time I lectured Paden about why Parker was about to get the spoon. He'd already had it, but the explanation still seemed to keep his attention. Parker got the 12 on his bottom (half to each cheek), then one on each leg, and a couple of each sit spot. He was crying hard when I finished, but still just crying, not close to bawling yet.
After Parker had a brief, private cuddle, I invited Paden to join us again. He was barely sobbing anymore, but was still willing to join us.
When Parker had calmed down, I put the two on their feet, and offered them the choice between ten minutes in the corner or no video games the rest of the day.
They didn't quite run to the corner, but...