The lemon juice will stop the fruit from going brown. Then carefully spoon all the fruit salad back into the scooped-out melon. If the melon keeps rolling around, you can ask your grown-up helper ...
Put the lemon zest and juice in a large bowl with the sugar and boiling water. Stir well, cover and leave for 24 hours Strain through a fine sieve or a piece of muslin and pour into sterilised ...