Family‑friendly dinner at your hotel or a popular chain like Barbeque Nation (if open and preferred by family) which has wide options suitable for kids.
Boat rides generally operate till about 6:00–6:30pm in some seasons; if your arrival is slightly later, consider a short evening lakeside walk instead — confirm with hotel.
Short visit to Jagdish Temple (open morning–evening) and wander the nearby bazaars for puppets and textiles — keep visits short so children don’t tire.