The United Nations Department of Economic and Social Affairs, Population Division issued a report on World Contraceptive Use in 2009 (report number POP/DB/CP/Rev2009). You can download the data in excel format: http://www.un.org/esa/population/publications/WCU2009/WCP_2009/Data.html. The most recent figures for Kenya are from 2003, but there is 2007-2008 data for Rwanda. The rates are broken down by conception method.
You can also find other data from the United Nations' unified database that allows you to search statistics collected by its various agencies: http://data.un.org.
If you search for the word "contraceptive," you'll get a few indicators of contraception use, including by age, marital status, etc.