If I remember correctly you will get a letter a month or so in advance from the Lord Chancellor inviting you to the event and asking you to detail up to 3 family guests. You are made very welcome, everything is explained in detail and you can't go wrong. If they still make the offer of a video, take it despite the expense! If you know someone who has got one, the video will give you a good feel of what's involved.
Congratulations and enjoy the day!
PM me if you wish.