To make this drink family friendly, simply omit the gin and the elderflower liqueur!
Put sliced lemons, tarragon sprigs and 1/2 cup of sugar in a bowl or pitcher. Muddle together firmly but don't emaciate the tarragon. Bruise it.
Add the water, fresh lemon juice and 2 cups of sugar. Stir until sugar dissolves.
Add gin and elderflower liqueur stir well.
Strain into a highball glass with ice or fill a shaker halfway with ice. Shake 4-6 ounces in a shaker cup and strain into a cocktail or martini glass. Garnish with tarragon and a lemon wedge