[{name:"name2",age:34,children:[{name:"childr344en1",studentid:137,},{name:"childr344en2",studentid:138,}]}]

db.collection.update({age:34,name:"name2",},{$set:{"children.$[element]":{name:"updatedname",studentid:123456789,}}},{arrayFilters:[{element:{name:"childr344en1",studentid:137,}}]})