What would you get for 4 yr old boy for £20?

[Disenchanted3]

I have £20 left for DS's birthday, So far we have bought him:

A book he wanted (perculiar pets)
A hot wheels stunt set
Hot wheel cars
2 small Iron Man toys
Animal snap cards
A Totoro hat

What would you egt with the last £20?

I know my mum has gotten him a scooter.

lego
bats and balls for garden

He loves books so maybe a nice set?

I would give him the money and take him to a toy shop to chose something.

Or something for the garden (paddling pool)?

Marne we took him today and he chose those bits but he was overwhelmed at the prospect of choosing at it got a bit nightmarish

lego - a bit at a time does add up.