Ueno Park is beautiful, and if you’re already going to the museums there’s a small tea shop behind the national museum. That’s really pretty in the spring. The ueno zoo also actually has many great cherry blossom viewing spots and large wildlife areas.
And for itinerary planning, using the Japan Travel Genius Course I think is a huge timesaver. Sample itineraries, custom guidance, language tips, etiquette details, and everything you could possibly need to know for a trip to Japan.
Japan Travel Genius