At the resort where the room block is, there are a handful of things you can add on to maximize your time during the stay including golf, putt putt, pickle ball, tennis, jet ski and boat rentals, fishing, and swimming. If golf grabs your attention, there is also a nice public course near Burnet called Delaware Springs.
Underground cavern tours and hiking trails
35 miles of hiking trails featuring a 60 foot waterfall, fishing, and underground caves
Drive an hour southwest from Horseshoe Bay and you'll end up in Fredericksburg (hopefully). Fredericksburg isn't quite Napa Valley, but there are a plethora of vineyards and tasting rooms that pair well with shopping and dining in downtown. * There is also another unique state park here (Enchanted Rock) but I already have put two of those before this