I took a family trip to Japan last year, and Osaka was a blast! Universal is definitely worth it, but outside the parks, check out Dotonbori for amazing street food and the Osaka Aquarium.
If you’re heading to Tokyo, the teamLab Borderless art exhibit was a huge hit with my kids, and Akihabara is a fun spot to explore, even if you're not into anime. For some good itinerary ideas, https://explorejapannow.com/2-week-japan-itinerary-for-families-with-kids/ was super helpful for us.
It’s got a nice balance of fun stuff for both adults and kids, plus some off-the-beaten-path ideas that really made our trip.