Two things that have annoyed me as a parent in recent weeks.

First: we went to the zoo with our two children yesterday, and it was excellent. However, liberally dotted around the zoo were machines selling plastic balls with little toys inside. Every time he saw them, our youngest got the hump because he couldn’t have a toy.

When we got to the exit, a direct door to the car park was deliberately blocked off by a promotional sign, forcing us to walk through the gift shop.

Second: our local supermarket regularly puts cars and branded toys on the end of aisles, separate to the specific toys aisle. The same effect: our youngest goes bananas when he can’t have one.

The key point: deliberate placement of these things to provoke pester-power from children, which feels cynical on the part of the zoo / supermarket – even if they’re hardly the only offenders.

But this, I think, is one of the reasons I feel so unsettled about the use of in-app purchases in apps for kids.

Because I can keep my password safe, and lock down my IAP settings on my iPhone and iPad before handing them over to my children, and so avoid becoming one of those parents who gets hit with a hundreds-of-pounds App Store bill.

But I can’t stop my kids seeing the IAP, and wanting them. Too often, IAP in children’s apps feels like just as big a pester-power stimulator as those end-of-aisle toys or zoo ball-machines.

This is a slightly difficult thing to write. In my day job as a journalist writing about apps, I’m excited about IAP as a business model, when it’s done right. Tiny Tower, Infinity Blade, Bjork’s Biophilia, Draw Something, Angry Birds Space, Paper…

These don’t feel cynical to me, because I can choose to pay or not to pay, and still enjoy the apps. I understand that IAP is a way to speed up my progress in games or add supplemental features to apps, but not essential. But I understand and accept this because I’m an adult, not a child.

There are various examples of IAP being used in apps aimed at or which will appeal most strongly to – a subtle difference - children. Smurfs’ Village and Ice Age Village are FarmVille-style social games where you can buy virtual currency, while Peppa Me Books is a collection of interactive book-applets that cost £1.99 a pop in-app.

Dr. Seuss Band is a musical instrument game based on The Cat In The Hat and co, where you can unlock more instruments and effects by paying. Twinkle Twinkle has a song pack and games unlockable for IAP and so on.

I’m not saying all these apps are bad or nefarious for their use of IAP. More that as a parent, if I like them I’d prefer the option to pay a one-off or recurring fee to get rid of the IAP and make everything available to my children.

Dr. Seuss Band has an ‘unlock everything’ option, actually. But for something like Peppa Me Books I’d happily pay, say, £1.99 a month for a subscription that gets me a new book every few weeks. And let it be said: I think both these apps are marvellous, so I’m not having a go at their developers by singling them out.

For Ice Age Village, perhaps a similar subscription could get you a set amount of virtual currency that’s replenished every week – which would at least be teaching my children to budget rather than to pester.

These models are coming through. New stories app FarFaria is planning to charge £2.49 a month for unlimited access to its content, so children will never encounter a paywall barrier or be prompted to purchase.

Outside apps-land, web virtual world Moshi Monsters also uses a subscription model: parents pay a monthly fee because they trust that their children won’t be pushed more digital purchases (although, admittedly, they will see the branded magazines and merchandise when we’re trundling around the supermarket).

I think there’s a selling point in ‘your kids won’t see IAP’. It’s certainly a message being transmitted by publishers like Toca Boca, whose Toca Kitchen lists as one of its features “No in-app purchases”.

Although here, too, there’s a grey area when it comes to publishers putting buttons in their apps promoting the other apps they have available.

A useful service for parents who might be interested in something fresh from a publisher they trust, and an important way for those publishers to make enough money to continue making great apps, yes. But also a possible pester-provoker.

I’m genuinely conflicted, as you can probably tell. I don’t think IAP in children’s apps is evil - at least, not most of the time. But it often makes me feel… unsettled. And it’s something that’s become pretty controversial in the US, where Apple is facing a class-action lawsuit over ‘bait apps’.

Perhaps I should treat it as a helpful way to teach my children that they can’t always have what they want, even if it’s a flashing icon on-screen promising new things for their favourite iPad app.

So this is a conversation starter really: what do you think? If you’re a parent, how do you feel about in-app purchases in apps aimed at your children?

If you make apps for kids, how are you approaching this, and what sensitivities do you see? And whoever you are, what do you think Apple should be doing about this area, if anything?

It would be good to get a reasoned debate going…