capacitive touch film or integerated capacitive touch panel display? using under glass
Depending on the specific LCD you use, you may find that it will have a layer of glass on the front of the assembly. Adding a further 2mm of glass may push the touch screen over the maximum sensing distance. LCDs with integrated touch panels may or may not be designed to work like this, so it would depend on the model you choose. I have seen datasheets that specify a range of lens thickness that they will work with.

If you use a touch film, you may have more luck. Although I can't see any spec. for touch distance on the one linked. Ideally, you would find that out before committing.