Your accountant would be a good place to start for asking this kind of advice which can get complicated and there are some potential pitfalls. Getting advice from a forum when large amounts of your children's inheritance could be at stake if you get it wrong is not a good idea.
There's absolutely nothing wrong with monthly dividends - ignore those scaremongers who say otherwise. If you've got the right paperwork in place, a monthly dividend can't be challenged. It's the "law" that matters and there's no law to prevent it, whatever HMRC inspectors and some accountants may like to think otherwise. There's no such thing as "spirit" - if Govt and HMRC wanted to stop monthly dividends, they could change the law accordingly - monthly dividends have been happening for decades, so they've had plenty of time to stop it, and even if they do change the law, it will only apply to future dividends, not past.
The real crux of your question is to get the paperwork right. That means doing a formal dividend waiver IN ADVANCE of each dividend being approved by the Board of Directors. If you do a google search on dividend waivers, you'll find a host of information about how to do it and the correct form of the paperwork involved. Apart from making sure the paperwork is right, you also have to show that the proposed dividend could have been paid to all shareholders if it weren't for your waiver. For example, if the company has £10k in reserves and you each have 50% of the shares, you can "waive" your £5k dividend, but your partner can only have his £5k - he can't have yours as well to give him £10k. Of course, that leaves £5k in the company, so in a couple of months time when the company has earned another £10k, it has £15k in reserves, and can pay £7.5K to your partner if you waive yours, and so on.
Another alternative would be changing the memo & articles to facilitate alphabet shares instead of equal right ordinary shares. You'd have B shares, your partner would have A shares. You'd vote a dividend of £10k to A shares and £nil to B shares. Just watch out for the settlements legislation - S660 etc - as if you're not legally married, you won't be protected by the inter-spousal transfers exemption so could fall into the settlement legislation traps - you'd need to do some research.