Bad idea to get malar implants and infra orbital implants separately?

It is very difficult to answer your question without in person consultation or, at least, series of appropriate photos. Depending of your condition, it may be quite possible to solve your problem with one set of properly selected implants? I do not see the reason why you must have two separate sets of implants? In person consultation with a board certified plastic surgeon with good reputation in facial implants is recommended. Good luck.

In an ideal world (not the one you appear to be in currently) you would get custom combined infraorbital-malar implants that optimally treat the underlying bone deficiency in a comprehensive fashion. But whether staging standard implants to treat it is a good or bad idea depends on the nature of your problem which remains unknown.