In view of the fact that there can be quite a bit of difference in how various programs approach Junior Day, I'd suggest that you try to find out in advance what approach a program takes before you accept or decline an invitation.
To give you a sense of the extreme we encountered: one program used Junior Day to speak to a very select group of players and their families. That school actually put on 2 Junior Days; one that featured a practice, another that showcased a game, and they gave invitees their choice of either. At that school, only about 6-7 players and their families attended each of the two days. The schedule afforded players and parents, alike, a generous oportunity to get to know the school's players and coaches.
At the other extreme, another program invited approximately 60 players and their parents. We declined that invitation, in part because we'd already attended one that hosted around 30 players. We felt like that was simply too large to come away with a good feel for what the program was really like.