Yes, if they are the SKS Chromoplastic (aluminum sandwiched between plastic) they are very easy to drill thorough and shouldn't give you any trouble delaminating etc. I have drilled through them before to install fender mud flaps. SKS's own instructions read explicitly that you must drill in order to install their aftermarket fender flaps. However, for this application, I would either fold that tab flat or cut off the part that sticks out and leave the riveted part in place. Then drill a hole through the fender and the riveted plate so that it still has some good support in that area. If not, then remove the metal bracket altogether and sandwich the fender with some other metal sheet for support. That's how I'd do it.

But if you're like me, you've grown impatient and by the time you're reading this you've already done something about it that perhaps you wish you hadn't.