I like that idea Stew
My kids liked peas, they still like peas....and spuds.
Potatoes get huge though as they sprawl, and they don't need a greenhouse, just something with soil in it. I have had really good success with bins or those growing tubs things made out of tarpaulin like stuff.
How about a growbag though ? You could plant three different things in that with her...Stew's French beans, tomato and something from the sweet peppers family.
Herbs are good with children too. Mint, lemon balm (she can make her own perfumed bath with that) chives (and mind the flowers can be seperated and sprinkled through salads or top soups for a little oniony flavour burst) and the like are pretty robust, while plants like basil are very tasty and grow quickly in a glasshouse if there's enough sunshine.
I bought one of the cheap plastic greenhouses from poundstretcher a few years ago. It was surprisingly effective...you might need to peg it down though if it's windy where you are.....and we got a lot of good stuff from it. I think it cost me all of £3.99. Didn't break the bank, then I found a tall hexagonal one in B&M's for under a tenner, and it was worth it for the staging racks alone. I think every seed we sowed sprouted in that
Back to the herbs though, you might find she'd enjoy a herb garden, thyme, lavender, rosemary, etc., there's a lot can be done with those and they'll thrive fine in our climate too.
Good introduction to both making food and making simples.
For fruits, I'd buy her a strawberry plant
and if you have the space nearby and don't have any, let me know and I'll send you some of the wild strawberries. They're as hardy as old boots, and their fruits are tiny, but they're little flavour bombs and they'll fruit from the end of the frosts right through to the start of them. They always have a sweet present for anyone who visits them
The other fruits that are excellent for children (because they're hidden under the leaves and the children look up) are raspberries and blackcurrants, but they both need space that the strawberries don't.
This thread pleases me so much; I love it that you're thinking of and doing this, with and for her
M