I have in my file next two families Sladovnik:
1/ Josefa Sladovnik * 1821 widow past Johan Sladovnik from Uboc emigratrated 1881 to USA with children Sebastian * 1861 and Anna * 1852.
2/ Vaclav Sladovnik * 1841 from Dolany with his wife Johana * 1839, son Josef * 1867 and father Johan * 1801 emigrated 1870 to USA.
Both towns are in southwest Bohemia between Domazlice and Klatovy towns. Kunes in common surname in this region.
Maybe your ancestors were from this area.
All the best.