There are lots of cup cake recipes on-line if you google "chocolate kidney bean cake" they are all basically the same but some use honey whilst others use sugar or stevia. This one has a half cup of honey as the sweetener:
http://www.bbcsouthafrica.com/recipes/?recipe=kidney-bean-chocolate-cupcakesyou'll see this one is beans and eggs mainly so double protein and not much else really
It also has the recipe there for choc avocado frosting with peanut butter which is a healthy fat hit, if he doesn't like avocado or nut butter you can make frosting with cocoa powder and cream cheese, don't need anything else although if you wanted to sweeten you could add icing sugar or mashed banana for instance. I never make frosting though although I've used just cream cheese before and no one seems to mind it's not sweetened.
The cakes I've made freeze well, I make sure they are interwoven with baking parchment so that I can easily lift out the number I need rather than risk them sticking together.
You can also use chickpeas instead of kidney beans. There are recipes for choc or choc chip chickpea cupcakes on line too (if you use only cocoa powder there is not sugar, I don't know if it bothers you or not, obviously adding chocolate or chocolate chips means there is sugar too).
The other cake I mentioned was white bean, again lots of variations on-line but here's one:
https://www.eatsomethingsexy.com/white-bean-vanilla-cupcakes-with-coconut-cream-frosting/this one you can use butter instead of coconut oil if you don't have coconut oil and it looks like the one I made but I decided to just throw in a random amount of ground almonds which worked fine.
They are all easy recipes to make really - use drained canned beans for ease. Fill the cake tins quite full rather than expecting a huge rise on them, and I struggled with mini cup cake cases, they got stuck so I'd suggest no cases but straight into an oiled cup cake pan.
they're still in 12-18 months trousers but they keep falling down
Oh you're not alone there. This summer DS wore age 3yo trousers as shorts, he is 6.5yo! i learned not to throw out trousers when they are too short, just save them a few years and re-use as shorts!
These belts are brilliant, we've been using them a good few years now, they clip onto the belt loops so you don't have to keep fastening and unfastening every time they go to the toilet so the kids can be more independent. There's a red and navy pair you get two belts in a pack:
http://www.jojomamanbebe.co.uk/2-pack-potty-training-belts-b6074.htmlthese belts plus always buying trousers/jeans with the button elastic and belt loops is how we manage.
I hope it's just teeth causing the problem. x