I liked Malaga more than I thought I would last year. I spent several nights there. But I was spending a month in Andalucia and had time to cover a lot of other places as well. I struggle a bit to suggest that someone with so little time spend multiple nights in Malaga. I would focus on other places. Can you not get value from your time-share points in some other way--during a domestic trip, for example? Lodging isn't so terribly expensive in Spain, and I think Andalucia will not be particularly costly in April 2021 unless you're traveling during Semana Santa. You can take a look at booking.com to see what you might pay if you weren't trying to go the time-share route.
That said, there are attractive side-trips possible from Malaga. Definitely get hold of a guidebook with good coverage of the region so you can make the most of your time, taking into account both your personal sightseeing preferences and time required in transit. For places on the AVE line heading north the train will be much, much faster than driving. For other places with train or bus service, driving will probably be as fast or faster (but don't discount the hassle factor and parking difficulties and cost).
Ultimately, you'll need to decide whether it's more important to you to see your top two or three places (with perhaps a substantial part of your time spent sitting in vehicles) or to be efficient travelers, seeing as much as you can (but perhaps not all of your top choices) with less time spent on transportation.
Granada is worth more time than just a day-trip from Malaga. The Alhambra alone can take a major chunk of a day. I think a lot of tours allow about 3 hours, but they certainly do not cover the entire complex. And there's a lot more to see in Granada. ViaMichelin.com gives a driving time of over 1-1/2 hours (train time is much longer according to the current schedule and trains are too infrequent to be practical--perhaps just due to COVID-19), and that doesn't cover any stops, traffic issues, searching for parking, etc. If I were going to take just one day-trip from Malaga to Granada, I'd want to get a very early start. There are of course bus tours available, but I wouldn't want someone else determining what I saw in a major city like Granada and how much time I spent at each stop. With a group the size of yours, even an expensive car rental would probably be less costly than all those tour tickets. Note: Alhambra tickets sell out very, very early, so you'll want to take care of those as soon as you can after the April tickets go on sale. The cost of direct tickets is modest enough that I wouldn't hesitate to buy them even if a bit uncertain about the trip; if you wait too late and the direct tickets are sold out, you'll be paying a great deal more to get into the Alhambra.
Antequera (where I've never been) is about 25 minutes by fast train (can be pricey if you don't buy the ticket early) or 1 hour by slower/cheaper train. Driving time is close to an hour. I think I recall reading here that Antequera's AVE station (Antequera Santa Ana) is a bit outside the city, so you'd need transportation from there to the historic district. I assume there are buses and taxis.
Use the Renfe webiste for trains: https://www.renfe.com/es/en
Out of space; will post more in separate message.