We live in a semi with a relatively small garden, and have an allotment. At the moment we have a hidden corner of the garden which we've turned into 'the farmyard' - a big aviary with a corrugated plastic roof and deep litter - in which we keep our pet hen and rabbit. We started off with 2 of each animal, hens separated from rabbits, but a visit from a fox climbing all over the aviary resulted in one hen and one rabbit dying of shock. The remaining hen and rabbit were gradually introduced to each other, and are now firm friends. The rabbit thinks she's a hen now, bless her - and even went broody sitting on eggs at one point during the summer! They roost together at night on top of the rabbit hutch, as the hen no longer uses the hen coop.
There is plenty of space left in there to comfortably house more rabbits or hens or quail, as it was built to comfortably house and exercise 15 hens, just in case, with an eye to the future.
On the half allotment we have next to our vegetable allotment we keep 4 hens for eggs in a tractor which is easily suitable for 10 hens.
All of our hens are let out to free range whenever we're around to protect them - there are far too many foxes around (day and night) to just leave them to it.
There is a reasonable amount of space left both in our garden and at the allotment to keep more livestock. The advantages of having them at home, of course, is that we're able to care for them more intensively. But there is plenty of space for lower maintenance livestock at the allotment, and there is a pretty positive response to poultry there - both from the committee and the plot holders.
We would like to branch out into something to raise for meat next year, and so are beginning to fact find now to give us plenty of time to learn, train and prepare.
Can anyone advise us as to what would be best for our circumstances? We'd love to get some chicks in and raise them. But as we're in a semi, completely surrounded by neighbours in a very urban setting, we couldn't risk any cockerel crowing! And presumably by definition one has no idea what sex chicks are when you get them. As we'd be looking at them being about 16 weeks old before they met their destiny

If so, perhaps ducks would be a better option for us? I find the idea of ducks more intimidating, but I'm probably being silly.
Another possibility we've played with is a couple of geese at the allotment, in a reinforced fruit cage along with the hens on the half allotment we have which is grass and orchard, but with separate housing. In my teens my family had a smallholding, and one of my chores was to feed and shut in the geese and hens. My favourites were always the geese - I loved them. But I didn't have to kill or pluck them, or do anything complicated with them which would involve handling them, so I strongly suspect I didn't see the 'darker side'

They co-existed very happily free ranging with our hens and ducks - but then they had a big field and pond to live in. So I was wondering if a half allotment would be too little space for them to get on happily together?
As you can see, we're very much at the 'dreaming' stage at the moment, but are wanting to find out some facts to give our various dreams a reality check, and begin to see what would be a viable route forward. Hopefully someone can give us some good advice to set us on the right track.