Is Y5V okay for decoupling capacitors?

You may also want to use more caps or higher capacitance and/or voltage rating than with X5R or X7R, as Y5V capacitance has a dependence on applied voltage as well as temperature.

Decoupling would be about the only thing I would consider using Y5V for (and only if I didn't have X7R or X5R available).

8p seems expensive. In large volumes, MLCCs in surface-mount should be a fraction of that price.

If the application must operate over a wide temperature range Y5V is not recommended.