My Hillie is a gentle, biddable creature (though has a mind of her own and excellent communication skills

) and I can completely trust her with children. Her first daughter Plenty was the sweetest creature you could ever meet. Her second daughter Katy is an oaf, no malice but a clumsy clutz and I would not be comfortable with small children around her in case of accident. (Hillie and Plenty both seem good at proprioception, I'm not sure Katy knows where her arse is half the time.).
None of my Jerseys would ever kick unless under severe duress. And probably not even then, except maybe Katy.
Using a good beef bull, one that's known for producing good calves off dairy cows, you'll get a very decent beef animal from a Jersey. And your Jerseys will stand for AI, which might be less feasible with Dexters unless you have a crush. So you can use a very good bull for under £20, and no risk of bringing disease on, etc. We used to use the local AI guy that did the local dairy herds, so he had bulls that were good for that purpose.
The Jersey has a particularly spacious pelvis, so is able to birth a larger calf than any other breed

. I always put them to Jersey or Angus first time, to give them an easy first time, and then anything I want after that. Plenty had two spectacular calves to our own Angus bull, one was even good enough to be entered in the Native Breeds class at our local mart. And we had four very nice offspring using North Devon (Red Ruby), which I think is my favourite. Yes the backside isn't as full as it would be from a full-on beef animal, but the Jersey has a bigger frame than a Dexter, so I would think the meat returned from a Jersey x beef is greater than from a full grown Dexter. (I'm sure it is, from the size and shape of the animals, but don't have deadweights for both to compare.). I've also used British Blue, which a lot of people do - they grow well on Jersey milk. And I've heard of people using Charolais too. Our neighbour, who used to have a prize-winning dairy herd of Jerseys and Guernseys (and of whose favourite cow Hillie is a descendent) used a Murray Grey bull.
And Jersey meat tastes
awesome. Knocks Dexter into a cocked hat.