We make a sort of cereal cake as follows:
Melt 125g (5oz) lard or dripping. Add approx 150g (6oz) dry fruit (raisins, sultanas, currants, chopped peel but not candied peel) and the same amount of dry porridge oats (not Ready Brek - just plain oats). Mix thoroughly with enough boiling water to make a stiff mixture. Measurements are approximate - once you've made it a couple of times you'll find experience will tell you how much of each ingredient you need. Either press it into a shallow dish, chill and cut into squares or let it cool a bit and form it into balls. You could probably form the ball around a wick as long as you make the mixture fairly stiff - I haven't ever tried. You can add alll sorts of scraps such as bacon fat etc, it's surprising what the birds will eat. When we have roast beef we save the fat that comes off the joint during cooking and use that instead of lard but you will find this makes a softer mixture that doesn't set as well.
Be careful using whole peanuts (never used salted peanuts anyway) as these can cause baby birds to choke).
The problem we found in using yogurt pots was that it was very difficult to get the mixture out of the pot in one block. We have made a cake using the above ingredients but omitting the porridge; we tried doing as you suggested and making a wick to hang it by or filling a half coconut shell with the mixture but the problem with that was that as soon as it got a bit warm outside the whole thing melted and fell apart before the birds could eat it.
We have found that the cheapest dry fruit is Sainsbury's or Tesco's own budget range - I think it's about 41p a bag. You can buy dry fruit specifically for birds but not only is it the same fruit, it's also much more expensive.
We used to use mixed bird seed or sunflower seeds in the cake but found that if any of the cake got onto the garden or grass the seed in it would germinate and we were forever pulling up seedlings.
Well done on giving this a go. It's completely ignorant to suggest that wild birds don't need our help.