It's not something that is easily answerable, sorry! It will depend so much of which force, which role he is in, things like that.
DP is currently working 'front line' in a busy London borough, he's been in about 5 years now. We have a toddler.
So the pros... Well, he loves his job, he really does. He is so much happier doing it than he was in his desk job. I am proud that he does a worthwhile job. His shifts, which are fixed on a rota, mean that I can work full-time too as he is around during the week - I couldn't work f/t if he was working 9-5 too. The money is ok, and there is a pretty good degree of job security (I know there are talks of cuts and redundancies but they aren't really considering making 20 and 30-something frontline police redundant)
We haven't had to a cancel a holiday and he is very, very rarely called in on a rest day, and even rarer that it is a 'you must' work on a rest day as opposed to them needing extra bodies and asking who wants to work. He doesn't do much overtime but I get the impression that is because he is in such a busy London borough that they have a lot of officers and so they don't get caught short the way some smaller places might.
I also really enjoy having time to myself, I'm so used to it now that having 4 out of 10 evenings alone at home is my standard and I get annoyed if he is around more 
The cons... Shift work isn't for everyone. If you're not used to it, it could make a very big impact on your life. Managing dinner time and bedtime alone for nights in a row. Sleeping alone. Keeping the kids quiet or out of the house during the day on weekends or school holidays so he can sleep. Him being exhausted and grumpy as he has just come off a row of night shifts. Court dates given about a week's notice and mucking up your childcare arrangements. The non-police parent more likely to be the one that pisses off work by being the main parent to take time off to look after the children.
Overall I wouldn't change it, I really wouldn't. But that doesn't stop be getting fucked off with his work, or lonely if I'm on my own with a toddler all weekend.
I think you need to a) find out more about the kind of work and shift pattern he might be doing on your local force (there are police forums that can help with this), b) think about how your work and childcare etc would sit around the potential shift pattern and c) talk about how big an issue it would be to your DH if he never did get a chance to do this.