Don't mean to rain on your parade. PPW is about relaxing but it's also about "showing off" all you've accomplished in the ~8 weeks since you last saw your family. There are lots of events -- some required of the plebes (e.g., parades) and some optional (e.g., tours of the ship in the yard, eating in King Hall), along with plenty of free time for you and your mid to hang out.
I-Day is really a day of nervous excitement mixed with a bit of fear of the unknown, unexpected, etc. interspersed with a few brief moments of being with your mid. USNA offers certain activities, such as the picnic and Supe's talk, for families but, unlike PPW and many other WEs at USNA, it's purpose isn't sharing USNA with your family and friends.
It's not my place to tell you what to do or not do. And, if your extended family wants to see USNA and be there for I-Day, go for it; I'm sure everyone will have a great time. I just want to ensure you're realistic in terms of what to expect and especially what your mid will be going through that day vs. the time that PPW rolls around.