Hello Grazie,There are two ways of handling this, depending on the situation and type of gathering.
1. If the guests, on average, are familiar with the area where the party is to be held and have their own cars, you can issue them with a detailed map, propose meeting places along the way, so that those with less knowledge of the area do not get lost or left behind. 2. Should they not be familiar with the area, or not have their own transportation, you can always retain the services of a shuttle from downtown Buenos Aires and arrange several pick-up points and times along the way, to suit the guests' different places of abode. This is particularly good if the gathering takes place in the evening.
That's how I have gone about it when organising family days at St. Andrew's Scots School in Punta Chica, in the northern suburbs. We have lots of people who come in from the southern suburbs (Temperley, Adrogué) and they usually use double-decker buses provided by the Headmaster of St. Alban's College. It is quite effective and makes everybody happy.
I hope this helps!CheersErnie