Avoiding clicks with changing biquad coefficients
Another possibility is to send the coefficients as poles and zeros and interpolate/smooth in the z-plane instead of the coefficient domain. This is always guaranteed to be stable. You can either interpolate in real/imaginary presentation or, if you want to get fancy, in magnitude and phase. The first one is a lot easier, since the phase interpolation has to handle wrap around.

Coefficient calculation from real and imaginary part is straight forward and suitable for real time. Only exception may be if you have a dual real pole/zero instead of a complex conjugated pair.