4 nights would be plenty. Ive been to USO and stayed at the HRH 2 times before, and Im going back with my family in December. Weve never stayed longer than 4 nights and we werent rushed at all (we went in August and May). I think its the perfect amount of time because you can devote one day per park, a day to do favourites, and then you get a bit of the last day to pick up the last minute souvenirs and maybe even do that one last ride on your favourite. It also gives you some down time, which is really nice.
As for the thrill rides, theres no shortage. But for your husband who doesnt like thrill rides, he wont be bored either. Im no thrill seeker by any means and I go on almost every ride at both parks. The only rides I havent been on and wont go on (due to a bad stomach for large drops) are Fire and Ice, Jurassic Park River Adventure, Rip-Saw Falls, and The Hulk. Every other ride is either a motion simulator (Spider Man, Jimmy Newtron), 3-D movie (Shrek, Terminator), Dark ride (ET, MIB, CITH, Spider Man), show style ride (Poseidons Fury, Twister, Earthquake) or river rapids (Popeye) and an action water ride (Jaws). Yes the Mummy is a roller coaster and it has one large drop in the end (and a few not as large drops), but its not that bad. If you do a Google search for The Mummy you should find stuff from when it first opened. Get your husband to read it and see what he thinks.
My thrill-rating of each ride Ive been on, based on a scale of 1-10, 1 being no thrill whatsoever, 10 being scare the pants off you is:
US
Shrek 4-D = 3. There are a few little elements that make could you jump, but nothing that would make a 5 or 6-year-old cry (in my opinion).
Jimmy Newtron = 3. Its just a room full of motion simulators where you watch a movie. Its a bit like being in an IMAX movie, only youre in motion simulators. Its really fun.
Twister = 2. The most thrilling part of this is when youre in the queue. I thought for sure something was going to start shaking or moving, but it didnt. You just stand in front of what looks to be a stage where they have one of the scenes from twister set up. Stuff happens all around you, but just remember that its windy.
The Mummy = 8. Anyone who says this isnt thrilling has got to be kidding. While it starts off all nice and dandy, it picks up about 2 minutes into it, and from there on in youre speeding up and down pretty fast. Since its indoors, theres no major twists or upside down bits. I only rode this one twice, and both times I closed my eyes on the last drop, and of course just milliseconds before the on-ride photo. Be sure to be on the lookout for a surprise ending.
Earthquake = 2. You know what youre getting yourself into before you even step into the queue. Theres a presentation about the movie and how they made it if you choose to see that before you do the actual ride, or you can opt to go straight to the ride portion. Its basically what would happen if you were in an earthquake on a subway.
Jaws = 4. It is pretty thrilling since you cant really tell when hes going to pop up, and where. You can sort of guess, but dont necessarily go by that. I think this one is pretty straightforward though.
MIB = 3. I say this only because some people might be prone to motion sickness. The ride does spin, but not a whole lot and the worst of it is in the end. Other than that its really great! You get to shoot aliens like youre in an arcade game. Its similar to Buzz, only better.
BTF = 6. I wasnt going to add this because it probably wont be around much longer, but if they keep pushing the close date back you never know. Its a motion simulator in front of a really, really big IMAX screen. Yes, the movie might be a little dated, but every time my Mom rides this she gets a case of hysteric giggling. Hopefully it will still be around if you go, it was/is my favourite ride (tied with Popeye).
ET = 4. Surprisingly enough, this ride has a few drops that made my stomach flip the first time I rode it on our last trip. You ride bicycles on a track. Its got a really neat queue.
Terminator = 4. Like Shrek, its a 3-D movie. There are a few surprises that might make you jump, but its nothing too bad. Its my least favourite ride only because Im not too interested in the Terminator. My dad really likes this one though.
IOA
CatInHat = 3. This one is great. It has a few spins, but they are pretty minor. You ride a couch through a life-size version of the book.
Carr-o-Seussel = 1. Its a carousel. Enough said.
One-Fish-Two-Fish = 1. You might get wet if you dont follow the instructions in the song.
Poseidons Fury = 3. If you can stand the usually long wait time, its pretty good. You just stand up in rooms while your tour guide tells you stuff. Theres a cool water feature though, and a good portion of the ride is in darkness.
Flying Unicorn = 4.5. Its a good roller coaster to get you introduced to them. If you want to ride the Mummy, I suggest starting off with this one first so you get the feel for them.
Popeye = 3. You get SOAKED. Be sure to put everything you dont want to get wet in the plastic covered thing. Its really fun without any major drops.
Spider-Man = 6. This one can be pretty intense. Youre in a motion simulator on a fixed track watching a 3-D movie. If it gets to be too much just close your eyes and its fine.
I hope this helps. You should really check it out. Theyre both great parks with some pretty awesome rides. Like I said, Im not a thrill seeker, but I can do all of those rides no problem. Theyre just fun. Your son would love it, and I have a feeling your husband wouldnt be bored either. If worst comes to worst, he could see the Blues Brothers (US), Bettlejuice (US), Horror Make-up (US) and Sinbad (IOA) shows. Plus theres lot of shops to check out. Be sure and let us know if you go!