Wavelet packet analysis, Sampling rate, Decomposition level
"My question is what is the best level of decomposition to see these frequencies?" 


You can achieve this through separation of the three components you have into different bands. Since the inner most level is a low passed version of the signal, you should try using at least 3+1 decomposition levels.

With dyadic scaling (the decomposition method typically used with wavelets) outer decomposition level covers the range of frequencies from F/2 to F .. The next level covers F/4 to F/2.. and the next level covers F/8 to F/4....etc.



Assume a signal of two sinusoids (0.4Hz and 1 Hz) with 10Hz sampling rate you get the following plot for its frequency content decomposition into 5 scales dyadic wavelet scales. by changing the sampling ratio, the location of the peaks in wavelets subbands change