Day 1: Delhi-Corbett (250 km || Approx 07 Hours)
Activity: Arrival in Delhi, pickup from Railway station/Airport, and travel to Corbett.
Accommodation: Check-in to the hotel.
Evening: Dinner and overnight stay at the hotel.

Day 2: Corbett – Nainital (60 km || Approx 02 Hours)
Morning: Early morning pre-booked safari at Jim Corbett National Park (optional, extra cost).
Afternoon: Check out from the hotel and proceed towards Nainital.
Accommodation: Check-in to the hotel and spend the night at leisure.

Day 3: Nainital (Local Visit)
Morning: Breakfast at the hotel.
Morning: After breakfast, start the sightseeing tour.
Activities: Boating at Naini Lake.
Visit the holy Naina Devi Temple.
Explore picnic spots like Naina Peak, Snow View, Lands End, etc.
Evening: Enjoy leisure time.
Accommodation: Dinner and overnight stay at the hotel.

Day 4: Nainital-Delhi (280 km || Approx 07 Hours)
Morning: Check out from the hotel after breakfast.
Travel: Drive back to Delhi.
Afternoon: Upon arrival in Delhi, transfer to Airport/Railway station for onward destination.
Additional Suggestions: Pre-Booked Safari: Ensure that guests are aware of the option for a pre-booked safari at Jim Corbett National Park and the associated extra cost.
Meals: Specify whether meals are included in the itinerary, especially for Day 02 and Day 03.
Travel Time: Emphasize the approximate travel times to manage expectations, especially during long drives.
Optional Activities: Highlight any optional activities or attractions that travelers may want to consider during their leisure time.
Climate Considerations: Advise travelers to pack accordingly, considering the climate of the region during their visit.
Emergency Contact: Provide emergency contact details or local assistance information for travelers' convenience.
Remember to stay flexible, as unexpected events might occur during travel. Overall, it seems like a delightful itinerary covering wildlife, nature, and cultural experiences.