Clipping the dark needle-shaped tips of your agaves, and removing these tips from the plant no higher than your daughter is likely to fall into the leaves, shouldn't reduce the agaves' relative fitness.

I do recommend against removing leaves from your agaves. While we do see many examples of the 'pineappled' treatment given agaves and sotols, we also see many examples of agave grubs eliminating landscape plantings and feral populations alike. Most likely these grub invasions are more to due poor planting practices and poor site selection. Nonetheless, these leaves are how your agaves convert the power of the sun into starches and alkaloids that it and your family can benefit from. These leaves are how your agaves maintain their relative fitness. Relative fitness is how they 'stave off' pest invasion. 

Among my fellow Sonoran Desert horticulturists, we ask each other: If parents are concerned about the prickly native vegetation, and many are removing it from their landscape when their children enter the mobile stage, are they also removing their stovetops, ovens, refrigerators, 2-cycle engine equipment, solvents.... ? You get the idea.

I'm glad to see that you are mindful of what your daughter is exploring, and attempting to make the least intrusive adjustments to the living community of plants around her until she's reached the stage of savvy junior natural historian.