I belong to Mathura. Depending on energy levels and time available places can be added /deleted
1.Krishna Janma Bhumi-No phones or car keys allowed inside.Lockers are available. Clean washrooms. Can take 2 hours easily depending on rush.There is Jhaki inside. Kids love it. Enjoy lassi inside temple premise and breakfast at Brijwasi, a famous local restaurant just opposite Krishna JanmaBhumi temple.
2.ISKON and Prem Mandir are almost adjacent to each other at Vrindavan. Rang Ji ka mandir is also a nice one. Fort style.
3.Dwarkadish temple is in holigate area which is old city. It has Yamuna river at walking distance. There is Brijwasi restaurant at entrance of Holigate entry and very nice jalebi, kachori wala on right side as you enter Holigate.Beware of monkeys. Very notorious. Do not hand carry eatables Or lookalikes else will be snatched by monkey in a jiffy.
4.Gokul is a full day.
5.Govardhan Prakrima is also a full day.
6.Ramanreti Ashram on banks of river Yamuna is a nice Ashram where you can see Sadhus and their day routine.
Nuego is an electric AC bus which runs now between Mathura and Gurugram daily twice.can be booked through redbus app. For local movement within Mathura enjoy e rickshaw as it is most convenient due to Narrow lanes. Feel free to call in case needed.
Thanks
Anil