At this time of year, outdoor activities pick up, the kids go swimming and so on. Best thing you can buy for the summer is a Towel Poncho. Seriously, kids love them and they can dry them or keep the cold off of them until they get inside.
eBay Store: Get Wivvit are selling cool Princess and Ladybird Towel Ponchos for just £4.99 including FREE delivery!
I LOVE the Princess one... put the hood up and your little one will look just like one. The Ladybird one is pretty smart too.
I take Towel Ponchos down to the beach with us in the summer, as they are so much easier for the kids to dry themselves.
They are great for when the boys come out of the paddling pool too. Sure, I don't find them the best for drying but they do the trick until the kids get inside to dry off properly.
For under a fiver, I think these are a good buy. They would even be nice to pop in with a gift.