Tell me about it. This is our first time going to UO and we only have a day. Since 4/5 of us are big HP fans, I got the two park tickets, plus we're staying onsite.
I look at the cost of this trip and think about how much I could get done around the house with that kind of money and I feel a little insane. I love these trips, the memories, the photos and the running, but it’s so much.
Okay, enough complaining out of me...
You probably don't want to hear this, but if your party has huge Potter fans, then they may want/need/require/plead for the interactive wands that allow you to cast spells at different locations in both areas. The good news is that you can buy one wand and then everybody takes a turn, but at least be aware. And if it's not too crowded, you should be able to adequately experience Wizarding World. I spent a day at USO in April 2017 and enjoyed it. I didn't come close to seeing everything, but I also chose to focus over half of my day on Wizarding World shows, attractions, food, etc.
In my opinion, the value of a day at Universal especially with the park hopper tickets depends entirely on how much you either love the franchises represented there
or outstanding themed entertainment. Many of their attractions are very well done, on par with what you find in Disney and arguably better in the case of Wizarding World.
If you love Harry Potter, it is spectacularly well done. IMO, Wizarding World also offers substantially more to do than Pandora. If you don't love Potter, but appreciate a very well done thematic experience, then Wizarding World fits the bill as well.
And if anyone loves dinosaurs/Jurassic Park, that area in Islands of Adventure is quite fun and you may even be able to meet a velociraptor. And yes, they act very much like they do in the two new movies. The raptor will try to scare someone in your group.
If you're ambivalent about all the franchises/IP in Universal, then it may not be the best value for you. In short, do your research and decide what makes the most sense for your group. And be aware that depending on the level of fandom your group has for Potter, that could get very expensive in food and merchandise on top of the park admission.
Now, a caution. I would not visit Universal the day before, the day of, or the day after any race. I feel this way entirely because you want to give your full attention to Universal on that day and one day before the race means you either must leave Universal early or you will get to bed late. Day after is tricky because you may want that day to rest and relax if at all possible. I went 2 days after 2017 Dark Side and it worked fine although I was still tired from the races, I was also able to fully enjoy Universal at whatever pace I felt like after the races.