Warnings, and "what did you learn?"

The other day we went to McDonalds to play in the playplace. There is a part that is for toddlers, and DS2 is really TOO big to be playing on it. We have been a couple of times, and I tell him all the time not to be on it as he climbs over the little kids and has knocked them down. Well, I told him not to go over there- there is a great big thing he can run around and play on! He listened at first, but went back. I called him over again talked to him about it, and he immediately went over and got on it- again. So... we left. I should have left after the first time, but I gave him a warning. I am learning quickly with DS2 that warnings don't work. Go figure, I should have learned that with DS1 but alas, I too take a while to pick up on SOME things! Anyway, we got in the van and the friends we were with then left too, but THEY got to drive together. DS was so sad, and cried all the way home. I sure hope he is learning something by all of this. But, I have to remind myself not to say things like "you need to learn to listen," or "what did you learn from this?" or even "I hope you learned your lesson." Because as Jim Fay says in Love and Logic, they then devote their entire life to proving that they in fact did NOT learn anything!