First of all, I believe that the seminars, which you mention, are of low utility to you, because such programs work well for people who do not have much international experience. You seem to have much of it, so I suspect that you'll not benefit a lot . All in all, they usually don't assess anything, being a very vague indicator of your abilities and commitment in general. On the other hand, you'll have the possibility of getting around some business schools, which itself is a very important thing (unfortunately the USA is not so small country).
On the other hand, you'll have much more fruitful experience if you embark on summer programs at Stanford ot Booth. The school name itself plays a grea role when evaluating profiles. You'll also have plenty of time to network and get close with your classmates there. But your biggest considerations, I suppose, is the tuition fees of these programs. We all know that they are mainly offered to raise schools' revenues in the summer and they definitely come at a great price. Some people claim that a $100k MBA isn't worth the investion, so what about a summer course that costs $10k. However, it all depends on you pocket...
I've been already admitted to the summer university at Copenhagen Business School, which seems to have a good reputation across Europe. But in my case, I have to prove that I am capable of coping with business issues, because my undergraduate degree is Law. Moreover, I've been also admitted to a seminar named "Energy and Sustainability", which folloows the summer univeristy. But I am more inclined to pursue my master degree here in Europe, so it is maybe a matter of preferred destination, in your case the USA.