You can certainly make money out of it and during peak times it's great but then you have to remember that the times that you will be busiest are the times when the children are off school - school hols, weekends etc.. so it can be hard on family life even though you are working together at home.
We stayed open throughout the first winter but decided to close for the second so that we could get temporary employment which provided a more regular income for us. You are still entitled to tax credits too so you won't starve even if you're working like crazy for little return in the early days.
There are licenses for everything so that can be a bit of a minefield at first. DH had to go on a course to gain his B11 for selling alcohol, you need a license for the property itself, a music license, gaming license, inspections by the fire dept and environmental health. There are certain notices you have to display - some are so outdated! You have to pay business rates as well as domestic rates, refuse collection is different, 1 TV license only covers up to 15 TV's then it changes. If the business is already established then most of this will be easy.
You get plagued by companies trying to get you to advertise with them. We were visited in the early days by a golf company and the sales patter sounded fantastic, we signed up with them (£200) for 2 years and never received a booking.
We get lots of freebies though as local attractions and shows want you to encourage guests to visit!
We looked at the South West but decided to go North because of the prices and the longer season. Have your IL's looked into Blackpool? I only ask because if they are looking for an investment then the general feeling up here is that once the decision is made for the super casino (due in December) then if Blackpool get it the property prices should rise significantly. Sony have bought the Pleasure beach and loads of money is being pumped into Blackpool by huge investors.
I'm really rambling now, there's too much info!! I do really like it but we are fortunate that we don't have a mortgage so for us it wasn't much of a gamble, we don't push the business as hard as we should (we're pretty lazy business people tbh) Make sure that you and the IL's have the same goal otherwise it could go pearshaped!
Any more questions just ask away!!