Based on the advice you've already been given, here's what I'd add:
1. Determine how many people in the group would actually benifit from the EP.
2. Are you guys ok doing single rider line?
3. If you have small kids and are using child swap, that is potentially two rides back to back for part of the group. Would this be enough for the ride junkies in the group to get their fix?
4. With planning, "rope drop", and use of single rider and child swap, you can get by without an EP. It's just more rushed, a little less relaxed, and usually involves more walking and backtracking.
6. The busiest times of the year an EP can cost close to $100 per person per day. It could potentially cost closer to $3,200 dollars for all 16 people to get EPs for 2 days vs $1,000 dollars for the 4 rooms. And you might be able to fit everyone who needs an EP into 3 rooms which would be even less. I think there are a few standard rooms they allow you to put 5 in if one is a child.
7. If you really don't want to go the room route, it would be less expensive to buy park to park tickets, buy only one EP for one day, and then focus on attractions in both parks with long waits on day 1 when you have the EP, then focus on shows, less popular lower wait time rides, and other non-waiting types of attractions on day 2 when you don't have it.
8. Consider also that park hopping is much much easier at Universal than at Disney. It's more like changing lands than changing parks. You can be in another park in under 15 minutes. Sometimes a ride in another park is actually closer to you than a ride in the park you are in. We almost never hop at Disney, but switch back and forth all day at Universal. It's great for if the weather turns bad because you have all the indoor options to choose from in both parks. It's also great for small children as you have all the play areas and kid's areas available to you in both parks, so you don't run out of things to do with them.
9. Look into the APH room rates and see how much that might save you. I'm not sure how many rooms you can book at that rate, but you can sometimes get some very good discounts. In addition, depending which AP you buy you can get food and merchandise discounts and free parking. It isn't a lot, but with such a large group, it could add up to saving quite a bit pretty fast. Only the person paying needs the AP to get the discounts. Many times the money saved on only one night covers the cost of the difference to get an AP plus some. I saved over $100 per night per room last summer. Honestly, it may have been closer to $200 per night as the rack rate was at the higher end during my trip. That more than covered the extra cost of the AP, and I got EP, and park discounts on top of that out of the deal.
10. Will having the rooms be something you actually use for naps / afternoon breaks? It might be worth it just to have a place to retreat to if you think you will actually use it. The kids might also want to hang at the pool and swim. I know for younger kids that can be their favorite part of a trip. If you think you would use the room, I'd look at HRH or RPR as those two are the closest walks from the park. I think I saw where someone clocked HRH as 4 minutes from hotel pool gate to the park gate. Our first trip we never intended on sleeping in the room. We were using it to store stuff and for changing wet clothes (another thing to consider, lots of water splash areas for kids in the parks and they get soaked). Then we had a medical emergency and ended up actually needing the room. It was great having it right there for us to use.