Erm, advice on max numbers for the "shake-it-all-about" parade...
Top tip; 1 X Male paternal type, 1 X Female maternal type, (1 of each grand paternal/maternal types) your siblings that are actually interested (rather than those rejoicing in gaining the bigger bedroom since you left), 1 X partner (optional) & 1 x "bezzy" mate who may join as a result of attending.
In short, think of others & yourself- you have to look after them & someone has to pay for their transport & accommodation costs. (ie: don't invite people who feel they should attend but cannot afford it).
Family "black-sheep", nutters & known lunatics should be kept to a minimum, although they are expected weekly by the security staff. The seemingly witty reposte: "there's a bomb in my car" is heard frequently & they are more than happy to call the anti-terrorist people on every available opportunity.
So far as I'm aware, as long as the numbers attending do not reduce anyone else's close relatives attending then there is seldom a problem. Ball-park figure? 6 on average- ask if you want to bring more.