what were his/her options for what to do? I realise that the slaves could simply be freed but I assume that would merely leave many destitute and vulnerable to re-enslavement- were there organised relief efforts? I am principally interested in the American South but am also curious about the Caribbean.
the slaves could simply be freed
In the US, it might not have been so simple. http://www.teachingushistory.org/lessons/SlaveryManumissionFreedom.htm says "Attaining freedom in the Deep South was not easy and by 1810 it was almost impossible to manumit slaves. ... By 1800, in South Carolina, it became difficult to manumit slaves. ... In 1820 laws were passed that stated slaves could only be emancipated by a Legislative act." http://www.virginiamemory.com/online_classroom/shaping_the_constitution/doc/drake says that, between 1723 and 1782, slaves could be freed in Virginia only by the legislature. Restrictions were added later. "In 1806, the Virginia legislature ... [required] every African American freed on or after May 1, 1806, to leave the state within a year of manumission or risk being reenslaved."
I don't know whether a state could have legislated against taking slaves out of the state, or would have, but with the US Constitution's clause on interstate commerce, I don't know that it would have been possible. (The Confederate Constitution made travelling with slaves explicitly legal: Article IV, sec. 2)
So you have to transport them to a free state ... except that some free states did not permit black people to enter the state. Illinois and Indiana certainly, and I think California was another; I don't know about other states. http://en.wikipedia.org/wiki/Underground_Railroad#cite_note-32 cites a page that isn't responding (or I'd quote it) and glosses it as saying "For example, in reaction to Black Loyalists being settled in eastern Canada by the Crown, the city of Saint John, New Brunswick amended its charter in 1785 specifically to exclude blacks from practicing a trade, selling goods, fishing in the harbour, or becoming freemen; these provisions stood until 1870.".
So you transport them to a free state that accepts them ... except that the destination may have had a vagrancy law, so can you find them a job? I don't know how many places had them at the time, but they were apparently popular just before being outlawed by the US Supreme Court in the 1960s.
Organized relief: have you looked at the Underground Railroad and colonization of Liberia? I don't know to what extent they helped at the destination; the Underground Railroad page inplies that they didn't much help.
Outside of re-enslavement, what challenges (like lack of education, contacts, property, etc.) did freedmen face and how did they deal with them?