How will they contribute? For a start, I think they'll be using an offline copy of Wikipedia, and secondly, they are not likely to have access to any other resources with which to research things to add to Wikipedia.
Connectibility will indeed remain a problem for some time yet.
They can contribute about their own culture, or they can interpret other useful world information into the local language.
Ec
You don't need a lot of references to participate in Wikibooks, Wikijunior, Wikiversity, Wiktionary, etc. Once you get past the wikipedia-centric world view, there are plenty of opportunities for OLPC children around the world to contribute to the WMF projects.
--Andrew Whitworth