For an early birthday present I decided to get Blake something called Grow Your Own Butterflies from Insect Lore. It's exactly what is says, you order the butterfly net and inside there is a voucher where you can order your caterpillars for the reduced price of £2.99 (that covers the postage).
The caterpillars came in their own little home with their food at the bottom. While they are in there you don't need to do anything. Just place them somewhere warm but out of direct sunlight as this could cause them to overheat and die.
Thankfully all the butterflies managed to survive my cats. It has been such an amazing experience. You don't often get to see butterflies up close in the wild. We got to see them grow and change. Once they turn into butterflies you need to feed them sugar water and fruit such as oranges and mashed banana. It's advised that you keep them 3-4 days and release them when it's at least 12c and not windy.