Hard cheese will be fine out of the fridge for 48 hrs.
Jacobs crackers can be bought packed in 3s ( Tescos about £1.20 ) so they won't go soft.
I have often taken a unopened tub of humus away with me with no I'll effects after unrefrigerated for 48 hrs
If you have cool back and ice packs obviously you that if not a carrier bag and a couple of bottles of water /squash three-quarters full ( expel the air or they will explode ) and frozen will keep things cold .
Do you have / can borrow a flask, a good quality Steel one will keep things hot for 24-hours with no problem so soups stews bolognese chillies etc all good to go.
Things that don't need refrigerating at all are obviously ideal
Bread - bagels , thins, croissants, pitta , tortilla wraps, nan.
Fillings - meat paste , hard cheese, tubes of squezzey cheese, no drain tuna , sardines , mackerel , spam , cornbeef,
Make sandwiches more interesting with - pickles , Branston, piccalilli, mustard salad cream , mayo.
Snacks - any fresh fruit , any dried fruit , ready sliced or individual bars of malt loaf
Individually wrapped cookies
Are you going to be eating at the venue or or in your hotel need to bear this in mind to see if you need to take a plate spoons and forks and perhaps a small amount of washing up liquid to if you have to wash things in your hotel room.