I love the sound of a garden and I don't want to discourage you at all. But I do remember hearing about certain parts of plants being dangerous to plant with young kids around. This is what I found... I'd make sure to do some more research before you plant.
While these are not poisonous plants as such - after all, we are encouraged to eat at least five portions of fruit and veg each day - certain parts of them can be toxic.
Remember: any unripe fruit or vegetable can cause stomach upset and generally affect the gastrointestinal system.
APPLE: the seeds/pips are toxic, containing cyanide.
APRICOT: the kernel, which looks a bit like an almond, also contains cyanide, and children have died as a result of eating a few of them. However, they do taste very bitter, so most children - if they even try eating a kernel - will be put off by the taste.
RHUBARB: while the stems are used for all sorts from jam to wine, the leaves are highly toxic.
POTATOE: unripe or green potatoes are toxic, as is the foliage. Hence the need to store potatoes in the dark and cut out any parts which are green before cooking.
TOMATO: the unripe fruit of the tomato plant can cause stomach problems, while the stems and foliage often irritate the skin.
STRAWBERRY: a number of people develop allergic reactions to strawberries.
BRASSILICA: these are vegetables such as cabbage, kale, brussel sprouts, etc. A number of people find them indigestible and develop allergic reactions to them. If your child really doesn't like sprouts, there might be a valid reason for it!
While a number of these 'poisonous plants' can and do at times cause serious health complications and even death, the majority don't have such drastic effects or have to be eaten in large quantities before they do much damage. However, it is best to be aware of any possible toxic effect a plant may have, especially when considering planting up gardens for young children. Don't let this list put you off eating apples!