i want a family dog and my children have decidid on these two breeds any feedback on these breeds would be great. the youngest of my children is 9. we live in a semi det house with a medium sized garden, and have fields just round the corner.
the dog would be on its own no more than 3-4 hours a day.

Really it must be you as parents who have final say on which breed you have as you will be doing the caring for it and will have the opportunity to evaluate whether you are suitable as a family for these breeds of dog ;) (as well as whether these breeds are suitable for you ;) )

Have a look here

http://www.the-kennel-club.org.uk/

Click on Breed standards and then on the different groups, there is info on the different characteristics of each breed, one big difference is the amount of grooming that they require, beagles have very short coats and are easy and quick to groom, cockers can be quite a challenge, especially as they get older and hairyer and they often need trimming/stripping out which you can learn yourself but is time consuming for some people ;)  both breeds have a reputation for 'going deaf' when they are on a scent and recall can be difficult, is this something you can cope with?   There are breed clubs listed on the bottom of the breed pages so you would then need to contact the clubs and arrange to meet you chosen breeds (discover dogs is a good place to go :) ) this can be quite an eye opener, seeing a dog in the flesh can be somewhat different to your expectations ;)

Hope this helps

Beagles dont respond well to being left.  They can make a lot of noise.  I usually take mine with me most of the time or if not leave one of the other dogs with her in the utility room or otherwise she would have eaten something in my abscence.  Apart from when they are having phantom pregnancies they are adorable and usually have excellent temperments and are good with other dogs.  A lot of people I know never let them off the lead as they are not good at recall although mine does goes of the lead as she follows the pack of dallies who do come back.

If you are thinking about a cocker remember lots of grooming.  When they are in full coat their paws are massive and they trapse lots of wet and mud through the house.  Some seem a lot hairer than others.  Make sure you check out the temperment of the parents as there are a lot of not so nice tempered ones which I have met.  Most of the ones I have problems with have been kennel raised the ones who are raised properly are quite nice dogs.  I do know quite a lot of people who work and leaves theirs.  I would also ensure they are not from the working lines.

As Dill says the best thing to do is meet both breeds both have totally different personalities and downfalls.  They might be the kids choice but remember you will end up doing most of the work for these dogs.  My eldest son wants a bloodhound for a pet ;)

Cockers can also be people orientated.  You should consider very carefully how to teach any dog to appreciate being alone.

I wasnt trying to imply that they were good being left alone digger far from it I dont think many dogs like being left alone especialy puppies it is just that I have a lot of my customers who do leave theirs all day.  I just feel out of the two the beagle is more likely to do damage and I do speak as someone whos family owned cockers previously.