Straight to your questions:
1. By default the Kendo UI Grid reads its data (makes a request to its read url) when the widget is initialized. This behavior is controlled by the autoBind property, which by default is set to true. So basically in your case the grids reads its data (default behavior) and immidiately after that a second request is made to filter. My suggestion is simply to set the autoBind property to false in order to avoid the initial request to load its entire data.
2. It is possible to access the master row (of parent grid) in the edit event of the child grid. This way one of the fields of the data item (child grid) can be set to a value extracted from the master row data item. Please refer to the http://dojo.telerik.com/evarE for a live demonstration of this approach.
masterRow = $(
//just for testing purpose the field "ShipCountry" of the child data item is //set to the EmployeeID of the master data item
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