I think it's totally normal for a boy, and no- I wouldn't be putting a stop to the tumbling around. He's probably just learning what is appropriate and what isn't and when it isn't. He still isn't 2 yet afterall.
I think a trial in the over 2's might be a good start but obviously if they're not willing to give it a go- what do you do?
The dummy- how do you think he'll go without it?