1) Who's "everyone"? Obviously they haven't been to Great America. I used to think MM was kinda trashy until I went up north. Yikes. Magic Mountain's okay. It's certainly not dangerous.
2) Depends on the kids. There's a whole section of the park dedicated to little kids.
3) Yeah, but it might not save you any money. Buying a ticket for MM is $40 online. Buying at the gate is $60 for MM, $30 for HH, or $70 for both. You can't buy a combo ticket or discounted HH ticket online so you'd still be spending a total of $70 to do both. And there are always discounts available from local merchants/hotels/etc.
4) Depends on what you like. I just went with some friends and we came to the depressing realization that we rate the rides on comfort, now, rather than thrills. "That one had great back support." The only ride that people told us was a must-do was X. Which, of course, is currently closed. I like Goliath. It's both exciting and smooth.
I have to say the park seems to be slipping the last decade or so. It's uncertain future isn't helping. (The parks are for sale as a group.) It seems like anything that doesn't relate directly to ride safety is being left to decay. Back in the 80s, they put TV monitors on many of the longer lines that showed loney-tunes cartoons and occasional announcements about the park's new and upcoming attractions. They've been dead for years. Lighting systems are in terrible shape. Panels hanging askew (that aren't supposed to be). Most of the photo booths were closed. A couple of restaurants were closed. Several of the small rides were closed with no sign that they were closed for repair...just closed. Several older, large rides were in the same situation. Freefall was shut down. Superman only had one track running. Gearworks looked scarier than any carnival tilt-a-whirl. The monorail had leaves and branches on the rails. They also haven't bothered updating the directional signs since installing the latest group of rides. Some of them point to dead ends.
It's kinda sad when I think back on what it was like back in the troll days. It had charm and the development of the park was well planned. Now it's jammed so tight with rides it's had to get around and there's no theme to the new stuff.
Still, it's the place to go if you want rides. I've got two more free trips and I'll have fun using them. I just don't go there expecting anything beyond the rides. For charm and presentation, I go to DL.
It was super hot as we walked out to our car at the end of our day, and the roudy teenagers getting their lunch out of their cars gave us a bunch of ice cold bottled water 
