We moved to Cornwall 8years ago. It's a lovely place - but the honeymoon period will eventually wear off so you need to be sure it's for you before you take the plunge.
There are plenty of positives about living here - it's a beautiful place, the schools are great, the beaches are the best in the world and there's so many to choose from, the people are lovely (most of them anyway!), and the pace of life is good. There is very low crime and we have in places the fastest broadband you can get anywhere.
However there are downsides -for me personally, there are hardly any decent shops and it's an hour from us to Plymouth or almost 2 hours to Exeter where there's a nice shopping centre.
Cornwall is a long way from anywhere else and it will be a big effort if you need to go "upcountry" to see family etc. You will also be inundated by friends and smoky who want to come and stay with you for a free holiday. This can be fun at first but gets on my nerves!
There are jobs to go round but lots of the work is seasonal, for example the cafe is a great idea but bear in mind that you will be busiest in summer and you will have to work long hours when everyone else is on holiday, which might also affect the time you can spend with the children? Then you will be much less busy in the winter when it's grey and boring!
There are fewer jobs here for the children and we expect that we will eventually relocate to done where more central when they are older and at uni, so we can be easier to get to.
I'm not trying to put you off but bear in mind it's not quite the same as people first imagine!
If your looking for a business have a look at the Miller Commercial or Scott Burridge websites to get a feel for what is out there for sale. There are lots of support agencies out there to help small businesses in Cornwall.
I hope this helps you and would really recommend that you visit lots before making your mind up, and come in the depths of winter too!