I second the idea of a disposable camera, perhaps with a small album to put the pictures in. Another perennial favourite is a torch. All 3 DGC love torches and musical things. Last X..S we bought a proper but small snare drum for 5-y-o DGD1 who had shown great interest in Grandpa's drum kit. He has given her a few informal lessons and she has now mastered the basics. She can also knock out a tune or two on her small keyboard. DGS and DGD2 also have musical instruments - recorder, ukulele, small guitar, mouth organ, keyboard, etc. No pressure or lessons just encouragement when they play with them.
Must say that the favourite toy of all last Christmas was the giant, inflatable, radio controlled, goldfish (you can get sharks too) which was actually a present for SIL. The Goldfish 'chased' the children around the house and slept on their bedroom ceiling. It also spent a lot of time floating about in the bay window to the amusement of passers by.