merge table into power query and keep greater date

One way:

1. Load the Users table into PQ (Connection Only).
2. Load the Add Record table into PQ - group on name with aggregated column using Date (aggregate = MAX).
3. Merge the Add Record query with the Users query on the Name field.

Please try

let

    Source = Table.NestedJoin( Excel.CurrentWorkbook(){[Name="Table2"]}[Content], {"name"}, Excel.CurrentWorkbook(){[Name="Table1"]}[Content], {"name"}, "Table1", JoinKind.LeftOuter),
    MaxDate = Table.AggregateTableColumn(Source, "Table1", {{"date", List.Max, "date"}}),
    ReorderedColumns = Table.ReorderColumns(MaxDate,{"name", "date", "age"}),
    #"Changed Type" = Table.TransformColumnTypes(ReorderedColumns,{{"date", type date}, {"name", type text}, {"age", Int64.Type}})
in
    #"Changed Type"

I was hoping that the OP would have a go himself without being handed a solution: he's had a lot of help on PQ so far and should have been able to follow my instructions.

Excellent - good news.