The official “things to do” site highlights the waterway: kayak or stroll along it. Great for a relaxed afternoon: shopping, dining, taking in nature + town center ambiance.
The Cynthia Woods Mitchell Pavilion is a large outdoor concert venue in The Woodlands. If your group enjoys music, you might plan for an evening outing here.
The area also offers nightlife, bars, social spots. Good for a “welcome dinner” or casual get-together the night before the wedding.
The city website mentions that Tomball offers “history and nature, live music, … unique shopping and mom-and-pop restaurants.” You could spend an afternoon strolling the historic downtown, browsing antique stores, boutiques & cafés. Good for a relaxed meetup with wedding attendees who have arrived early.