Hi Happy Girl - do you think the child is serious about it?
Firstly, €100 is not expensive for an acoustic guitar - it's cheap.
But there's no point splashing out if it's just a phase or whim that they will grow out of in a few months. However, they will certainly rapidly lose interest/confidence and will be put off if they are frustrated by a badly made low quality guitar that is impossible to keep in tune, awkward to play and has poor sound. Don't be tempted to buy sub €100 guitars. (I've never heard of Tenson BTW - but that doesn't necessarily mean anything)
Could you make a trip to The Sound Shop in Drogheda? The people there are knowledgeable, very helpful and they have a large range to suit every budget.
Whatever you choose make sure:
1. It is a steel stringed guitar (unless your little one was inspired to learn by classical or flamenco music - which is largely what nylon stringed guitars are intended for).
2. It is a guitar they feel comfortable with. Make sure they are not over reaching or that the guitar is too big or too small.
3.That if s/he takes to it and has talent, you are prepared to spend a few hundred euro not very far down the line on a better guitar - a €100 guitar will reveal it's limitations very soon to someone who learns quickly.
Good luck!