Glad you decided to count Granada in! It's a beautiful city, and a honeymoon in Spain wouldn't be complete without a visit. As everyone said, book in advance (Ticketmaster sells tickets that you can pick up at some of the ATMs in Granada or at the Alhambra itself). If you're looking for something a little different, the nighttime visit to the Nazari Palaces is fantastic and much less crowded than the daytime visits.
When you're booking a place to stay, be aware that the Alhambra and the beautiful old Albaicín neighborhood are on big hills -- and in the Albaicín, some of those tiny streets can get a little sketchy at night. If you just want to stop into the Alhambra and then move on, an overnight in a hotel up the hill next to the Alhambra might be your best bet.
If you're looking to spend more than a night in Granada, I'd recommend a hotel closer to the Plaza Nueva/Gran Via or in the city center. The nightlife in the city is fantastic, and be sure to visit a "tetería" (Moorish style tea house) while you're there.
As for your other destinations: Mallorca I don't know much about, though friends tell me it's worth a visit. 2 nights in Sevilla should be just enough to see the major hits (the cathedral and palaces -- fortunately, those are right next to each other). Madrid, Segovia and Toledo in 4 nights will be fast-paced but probably manageable (personally I might cut out Segovia, but that's personal preference more than anything else), and Barcelona is worth as much time as you can put aside for your visit!
And just one more note: You may want to start looking into other forms of transit besides the trains, since some locations (specifically, Granada) aren't all that well connected by train. Check out the Alsa bus lines (at alsa.es, I think). Their "luxury" buses are very comfortable, and for a lot of routes those only cost a few extra euros compared to the normal buses.
And finally: No matter how you plan this, it's going to be an amazing trip!
Last edited by l etoile; Jan 2, 2018 at 6:04 am