If there isn't one, we do/we'll do - zero and first conditional constructions

Question

The following quoted text is about using first and zero conditional constructions in the F2F ELL book. Please, find my question below the second paragraph.

Our children get their pocket money every week on Saturday. Of course we ask them to help at home.

In the following paragraph, the adverb usually suggests using zero conditionals which is used for situations that are always (in fact, almost always!) true, like habits and rules. There is not problem with this - it's clear. The issue (if you will) is with the last sentence. I understand it's in the unlikely situation, "they'll their children". But then this unlikely situation is also a rule! The parent is not talking about a specific situation in time (in real life), but a hypothetical case while he/she is talking about rules in their house. The question is: which is more logical (if both are perfectly fine in the context -or are they?):

If there isn't one, (we 'll tell them) that we're disappointed.

or:

If there isn't one, (we tell them) that we're disappointed.

And usually they do everything we ask them to do. And if they don't do it, there is usually a good reason. If there isn't one, (we'll tell them) that we're disappointed.

The following is the end of the text:

We strongly believe that this is a much better idea than the threat of no pocket money.

Update:

I think the reasoning is that it comes as a contrast to the "usual" case of there being a good reason which qualify for a zero conditional. Hence, the exception qualifies a first conditional (The usual rule is a back ground to the exception). However, if it were to come up in a non exception to a mentioned rule, then it would be a rule alone of something rare in which case it qualifies a zero conditional.

I would love to confirm this from credible sources, but knowledgeable and native speakers' opinions are very welcome.

Answer 1

I think you've understood all this fairly well. The use of first conditional "we'll tell them" implies that this situation never happens (or happens so infrequently that no example comes to mind). If it were the case that the children rarely have a good reason, zero conditional (rule of thumb) would be used. So essentially, first conditional is used for the last part to imply that not having a reason does not often happen, therefore differentiating from the rest of the sentence (which all happens regularly).

Answer 2

It's eight months since this thread was active, but I thought it worth reviving with a couple of ideas.

'Predictable or characteristic behaviour' is also the meaning of such descriptions of human habit as:

She'll go all day without eating. [...]

The parrot will chatter away for hours if you give him a chance.

Leech (2004.86), Meaning and the English Verb (3rd edn.)

Leech's second example has the traditional form of the first conditional sentences (will, if + present / If + Present, will), but the timeless meaning of the zero conditional. We see a similar example in (2) below)

1. If you heat ice, it melts.
2. If you heat ice, it will melt.
3. If it's sunny tomorrow, the ice on the pond will melt

(1) is clearly, in form and meaning, a zero conditional, with general/timeless reference, and (3) a first conditional, with future-time reference. In (2), however will with the 'predictable/characteristic behaviour' meaning has a timeless reference. I am not in favour of the 'zero/first/second/mixed conditional' labels but, if we are going to use them, I think that (2) must be labelled a zero conditional.

That being so, we have two possible interpretations of If there isn't one, we 'll tell them that we're disappointed. In the situation originally asked about (And usually they do everything we ask them to do. And if they don't do it, there is usually a good reason. If there isn't one, we'll tell them that we're disappointed), the 'll suggests 'predictable characteristic behaviour', and we therefore have a zero conditional sentence. If the conditional sentence has a different background (Their teacher has called to say they were not at school this afternoon. I'll ask them about this when they get home. I hope that there is a good reason for it. If there isn't one, we'll tell them that we're disappointed), we are now dealing with future possibility, and we therefore have a first conditional sentence.