Speak of the Devil.
I had thought about doing the full party kits but not sure if there was the call for this. There are companies that do the food as well but it gets expensive to set up for this and you have to do the environmentel health thing.
Have a good nose about to see what is on offer in your area. It might surprise you what is already available. Or there might be a gap in the market or it could be there is no call for it.
Market research is vital, compile a list of questions to ask. But remember to ask what would you pay. Parents love the idea of these things but when it comes to money they are often not prepared to pay all that much.
Its worth going to your business start up places and going on the free courses they run. The good thing about this kind of business is that its quite low cost to set up. Try to buy find suppliers that you can get quick delivery from so you don't need to buy in advance, it helps with the cash flow if you don't have to buy much until you get and order.
On the down side you are relying on word of mouth, even if doing it through a website it takes a while to build up the trust for people to place big orders to unknowns on the web.
If you go for it and get sorted out what you are doing, then TELL THE WORLD and his wife. Don't be shy, get business cards and leaflets printed up and carry them all the time. Stick them on every notice board you see. Be prepared to hand out a lot of cards before you get any interest. You might have to do a few freebies (or cost price) parties for friends and family to get the ball rolling.
Lastly go for it, what have you got to lose. At worst you will be left with a pile of party stuff that will keep you going for years.