If you are staying onsite which gives you the express pass for free, then you will have no issues seeing everything at both parks in two days. The same also applies if you are thinking about purchasing the express pass while there..however with 5 people it might be cheaper to buy one night at the hotel which gives you TWO days of express (check in and check out day).
If you are NOT going to buy express or stay at the hotel, you will have a harder time to see everything, but you will have enough time to see all the best stuff.
For IOA, you need to ride:
Spiderman
Popeye
Dudley Do Right
Jurrasic Park
The whole HP area
If you like Rollercoasters or big thrills, then ride Hulk and Dr. Doom.
For the Studios, you need to ride:
Mummy
Disaster
Jaws
MIB
Simpsons
T2-3D
Shrek
If you like rollcercoaster, then ride Rip Ride Rockit.
Of course this is not the whole list of rides for both parks, but some of the must do rides. If you have express, you will be able to do everything at both parks without issues.
I just pick a random night near the end of July and one night hotel stay would be $294. This would give you express for both days and a place to sleep for one night to get into HP early the next morning.
If you just bought express for 5 people for BOTH days, you total would be $500. As you can see, the hotel room would give you a BIG savings IF you were planning on purchasing the express. It always amazes me that people will spend the money to purchase express passes for two or three days, but they think the price of the hotel costs to much so they stay offsite. However, they are spending MORE money doing this. Its always best to look at all the different options
