A correction to my previous comment. Linear or Spline interpolation is not the way to go if you wish to decimate your data. The correct technique is, as you mention, to filter your signal before data decimation (dropping samples).
You are considering to use a Bessel filter. I assume this is because you want to minimize the time domain distortion of your signal. This could work but Bessel filters are not very steep and it will be difficult to keep a reasonable bandwidth and protect against aliasing at the same time. I would recommend you to use an FIR filter instead of the IIR-Bessel filter. The FIR filter is phase linear and well-suited for data decimation. You'll find the high-level VI in the Analyze>>Waveform Conditionning palette.
