Ideas for making a low key birthday sleepover 'special' (6yr old boy)

[LowLevelWhingeing]

DS1 (6) didn't want to have a big party this time. He's been to quite a few big parties recently and couldn't decide what he wanted to do. (TBH, I think sometimes he's a bit overwhelmed at big events, but that's for another thread )

I also have a DS2 who is 4.

Anyway, DS1's favourite thing in the world is playing with his cousins (i.e. my DNs) who are the exact same age as my two, they are very close and adore each other. So I've invited my DNs to come for a birthday sleepover.

The thing is they are great at playing together and just love bombing round the house 'killing' each other and I'm sure they would just enjoy being here, but I'm looking for ideas for more 'special' things to do with the four of them.

My SIL is going to come with them, so hopefully they will settle ok and she will be another pair of hands (and will bring wine).

Any thoughts? I have ZERO imagination

bump for the tea time crew... (and I may be back attention seeking for the evening lot!)

...and here I am, ba da bump!

A trip to DVD shop where they can all agree on a suitable film whilst they're munching popcorn in their PJ's? My kids love this!

Make-your-own icecream sundaes.

Clear glass: spoon into it icecream, and then let them add sprinkles, chocolate sauce, whipped cream, marshmallows etc. Feels very special. Dead easy.

Glowsticks for the TV-watching, going to bed bit.

In the morning, make pancakes in the shape of their initials (for some reason, absurdly special!).

A couple of cheap giant bubble wands from Poundland to play with in the garden - the sort of thing that's fun by yourself but SUPER fun with friends.