The special days are more in depth. Each school will be different but you typically still get the info session and tour. But then depending on the schools, you get more. You may get a student panel. You may have a club fair. At Penn State, they actually took us to the nearby Accuweather location for kids interested in meteorology. There will be academic department meetings, perhaps sessions for financial aid or study abroad. They’re better - but if you can’t go, you can’t go - and if you need to learn more about the campus to decide if your child likes it, then do the regular thing.
If he has an extra interest - for my daughter it was Hillel…for my son it was academics…admissions will always be glad to set up an extra meeting for you or you can reach directly - so you sort of create your own day.
It’s great if you can go - you meet other kids and you get the entire campus sell - and sometimes lunch is way better to make you think the food isn’t institutional…but I wouldn’t alter your life to attend if it doesn’t work out.
Good luck.