I'd exploit the EAL aspect. Maybe have all the children say Happy Christmas in their other language, and depending on where they are from a bit about what happens in their parents country, so sweets in shoes for Nicklaus (? Sp).
For an English child you could have them show how to pull a cracker - you would be suprised how many people don't know what they are. Don't forget Scotland has it's own traditions and I'm not sure about Wales.
In fact you could have them in airs saying 'Happy Christmas' to each other in various languages and then pulling a cracker, even cuter if you have a few in National costume / fancy clothes.
Instead of having a full Christmas Show/Nativity the school where I work has each year doing their own thing - songs, poem, dances, etc. It actually works really well and because each class rehearses individually it's much easier to slot rehearsals in - we even have them singing the songs when they line up for lunch, or for a few minutes after the register. It also means the class (and staff) are less likely to lose the will to live because there aren't long rehearsals going through the whole thing.
I normally work in Reception and the audience think the children are so cute we could get away with anything! However, we usually do a song and then a rhyme.
This year I'm spending some of my time in Y2. It's quite a difficult class and the Christmas Concert is filling the class teacher with dread. In a moment of madness I said if he deals with a Christmas song I'll do the other 'thing'.
I'm thinking of a poem or rhyme. If it was funny or had the 'ahhh' factor that would help. Lots of the children are EAL so some of them don't have particularly clear voices so the simpler the better.
Can anybody help with ideas about what they could do? I'm slightly regretting offering to help but SO want to get it right.