Creating interest using features and materials
Small pebbles often capture interest and these could be loose or made into a mosaic. A tile mosaic can also add interest through shape and colour and can be something you could make together. These could then be incorporated into paving or hung on a wall.

Creating interest with plants
Plants can offer great stimuli for a child's senses through their texture, colour, scent and form.

Forms: Topiary shapes, whether formal spheres or quirky forms, can create interest and fun in a garden. Some plants have interesting flower heads such as Alliums with their globe shaped heads.

Movement: Grasses like Stipa and Miscanthus are particularly good at providing movement in the garden as they sway in the breeze.
Textures: Interesting textures can include the softness of the leaves e.g. Alchemilla mollis (which also attracts children due to the water droplets which sit on the leaves).

Learning in the garden
You can use the garden to teach children, not only about gardening, but by providing an opportunity for creative development and an appreciation of nature and wildlife, and the cycles of life.
It is important to try and give children a plot of their own and their own tools, to encourage a sense of responsibility. They could sow simple seeds, water them and watch them grow. They could grow something that they could eat, to learn to appreciate where food comes from. Raised beds or pots can sometimes be easier for them to reach. By having this area close to the house, children will be more likely to keep an eye on the progress of their work, and easier for you to keep an eye on them.

By adding plants that attract bees, butterflies, birds and other wildlife, you can allow children to get up close to nature and be enthralled by it. You can encourage birds into the garden by offering seeds and fresh water.

You can also use the garden to teach numeracy and literacy in an interesting way. For example, you could paint stones with letters which can be re-arranged into words, or you could get the children to count the number of petals on a flower, or how many stems there are.

You could play other games, such as asking the child to find something beginning with a specified letter of the alphabet or to find something soft, or red for example.

Of course, their requirements will change over time. In the early years you will want them close by and they will need more supervision, but later on, they will be able to and often want to play by themselves and have time on their own or with friends.

Water in the garden
Whilst open water is beautiful and can attract interesting wildlife, it is dangerous for small children. However, you could install a closed circulating system such as a bubble fountain or have a small wall fountain with a grate over the water.

Large play equipment
If you do want a large piece of play equipment, consider screening it from the house using trellis or plants.

Safety
Safety is a big consideration in a garden and any tools and chemicals must be locked away securely. Also, take care that there are no fall hazards and sharp corners in the hard landscaping.
Some plants e.g. Foxgloves and Euphorbia, are irritants or even toxic if eaten and others have sharp spines e.g. Berberis and Pyracantha, so these should be avoided

Take care to clear up any cat poo as this can cause infections. It can be particularly bad in areas of newly cleared ground, gravel or sandpits. Try to teach your child to keep their hands out their mouth and to wash them after being in the garden as all soil carries tetanus which can infect through an open wound.