because someone down the road made a complaint and gave my car reg number to police
I highly recommend that you please check the whole thing thoroughly with police and/or through a solicitor, et al. before even thinking of applying for the BC.
The whole thing around this - i.e. that some random person down the road simply informed police that she/he "thinks" that a person was driving uninsured and without license sounds really strange. I am not suggesting your wife might have done things more serious etc., but please please, for the sake of future panic free life, check clearly by all means possible that there was nothing more to it that it seems.
I mean, if any random person, for no apparent reason, started informing police that someone is driving without insurance and license (how did they know??), without even knowing them personally, is really something that does not add up. Are you sure that is all they reported to the police and nothing more?
Or is it just because your wife has foreign looking face, and they wanted to inform "anyway" to police? If that is the case, then every single foreigner-looking person will have to be visited by police every moment in their life, by someone or other reporting!!!
Rather than getting into trouble later on in life after BC, please please check many times that all is fine with this episode. This application is not like any other visa renewal or even ILR.
I see many people here in these forums, saying they did not know driving offence is serious and hence they did not declare etc., after they have had a refusal and ban for any future applications... these things destroy everything in future.
Please please check again, speak to the police, get a solicitor involved, more importantly - please again talk to your spouse and check there was nothing more than what you think there is, and if nothing checks out, i would even recommend putting it in the application notes somewhere (like exactly you have written here in this post) (I am sure many may think is a bit more unnecessary) but it helps to give you that piece of mind, in case they do grant the BC, at least you have declared everything even if "may" not have been necessary please.
Or better still, leave it aside without applying for the next 3 years or so, like Amber says, and ask your wife to not drive anymore again until she gets her UK license!!!
This is my opinion. Its up to you to declare or not. Since it is your wife who is applying, and you may have children and nice family life going on, please do not spoil anything for future just because of this episode and not declaring it or investigating it thoroughly.