At 80% recovery on the RO, ...

At 80% recovery on the RO, you would require 95% rejection to reduce the Cd to that level and 97.5% rejection for the Pb.  Contact a membrane manufacturer and see if they think that is possible at the feed concentrations of 0.02 and 0.1.  For ions with a +2 valance you should get over 99.5%, but that is at much higher feed concentrations.  Rejection % goes down as concentration goes down.  I think an RO will probably do it.

As for pretreatment, it all depends on feed water.  Well water does not have the high TSS levels of surface water, so you may be fine with just cartridge filtration.  What is the TSS or SDI?

You will also need something to control scale.  If the flow is small and the hardness not too high, you could consider a softener.  The larger the flow and higher the hardness, you would want to look at using an antiscalant.