Using the formalism of Maya diagrams and ladder operators, we describe the algebra of annihilating operators for the class of rational extensions of the harmonic oscillator. This allows us to construct the corresponding coherent state in the sense of Barut and Girardello. The resulting time-dependent function is an exact solution of the time-dependent Schrödinger equation and a joint eigenfunction of the algebra of annihilators. Using an argument based on Schur functions, we also show that the newly exhibited coherent states asymptotically minimize position-momentum uncertainty.