Plan for 1 day per park you want to visit. If you stay at one of the three deluxe resorts ( Hard Rock, Royal Pacific, Portifino Bay), you get free Unlimited Express Passes for the duration of your stay, from checkin day to check out. This is Disney’s equivalent to FP, only you are not limited to using it on only 3 rides. You can use it on all the rides as many times as you’d like.
Hopping back and forth between parks is fast and easy. You can go from one park to another in about 10 minutes. Going to and from the resorts is just as quick and easy. There’s a beautifully landscaped walkway, or you can take a short boat ride. It’s about 5 to 10 minutes to Hard Rock, depending exactly where you start and end. About 10 to 15 to Royal Pacific, and 15 to 20 to Portifino which is the farthest away. There are also cyclists pulling rickshaws, you can tip to take you along the walking paths.
Universal also has their own version of DTD, on a smaller scale called Citiwalk. Unlike DTD which stands alone, Citiwalk is attached to both parks and the hotels. Citiwalk is made up of a movie theater, mini golf, shops, restaurants, a small splash pad, and a small stage for outdoor entertainment. It is close enough to the parks and the resorts that eating there for a meal is not an inconvenience. It is quick and easy to leave the parks to go to Citiwalk for lunch.
In general, reservations aren’t needed for restaurants. You can decide 5 minutes before where you want to eat.
We really love Universal because you can relax, take your time, and just go with the flow. We find it much more laid back than Disney.
Having said all that, really do your homework and make sure Universal is the right fit for your family right now. I feel your kids are at the most iffy age to go. Very young children and toddlers are entertained by all the play and splash areas. Older tweens, teens, and adults by the thrill rides. When you get to the elementary age kids it’s really hit or miss, with some loving it, and it not being a good fit for others. Many attractions can be very intense, dark, scary, or all of the above. Many rides have height requirements, and many rides cause motion sickness. I’m not saying don’t go, I’m saying have a realistic idea of how many attractions the kids will be able and will want to do. Nothing worse than getting all excited only to realize once there that the kids are too short or too scared to do very much.
Universal does have rider swap if there are any rides some members of the group can’t or don’t want to do. Though, it’s a bit different than Disney’s version. Everyone stays together and waits in line until it is time to board. At that point, you tell the attendant you are doing rider swap. The parent and non rider go to a room to wait while the other members ride. Then you switch out parents. The rooms usually have a place to sit and a tv playing some type of cartoon or movie related to the ride.
With a little pre-planning, you'll have a great time. Good luck.