Total Meltdown by Elle James

An elementary teacher during the school year, Lily Grayson hires out as an au pair during the summer in order to travel expenses-paid to exotic locations with wealthy families with children. When one of her students suggests she apply for a summer job with his family going to Costa Rica, she jumps at the chance. Despite her immediate clash with his father, she agrees to accompany him and his two children to the central American country.
Rich Texas rancher originally from Costa Rica, Antonio Delossantos, knows money can’t buy everything. He lost his wife to violence and he’s determined to save his children from a similar fate. When he learns his son’s school teacher is also skilled in Krav Maga military-style self-defense, he agrees to hire her for the summer he intends to spend in Costa Rica.
Lily and Antonio join forces when the children come under attack by terrorists who attempt to kidnap them to hold for ransom. What starts as a summer vacation in a tropical paradise soon becomes a race to survive in the jungles of Costa Rica.