Second Order Filter with DC offset
Is it safe to use a voltage divider with a voltage follower as shown?


Of course, you've put the opamp in an inverting configuration, with the positive terminal having an offset. Similar to a differential amp but with no resistors on the positive terminal 

Vout for U2 would be:

\$ Vout  = -\frac{R7 }{ R6}*Vref + \frac{R7+R6 }{ R6}*Vpos\$