My parents were at the Newport Folk Fest the year Dylan went electric. My Dad had been a fan since he was in college at Rutgers and he used to come up to New York to see Dylan play at Gerde's Folk City. Their sense of the folk festival was that people weren't exactly upset about the fact that he was playing electric, it was just that the sound was really bad (distorted due to a sound system set up for acoustic instruments), and that Dylan seemed really surly and only played a very short set. They said that they really didn't see what the big deal was until years later, when the incident achieved status as folk music history.
As for how many people were there at Newport, it's a big festival, I'll bet there's quite a few Mudcatters who were there! That British tour in 1966 would have also been pretty exciting - the live recording of that Manchester show sounds pretty rowdy!