Really cheap activity, decorating biscuits- packet of icing sugar about 99p and a pack of hundreds and thousands about 99p in aldi/ home bargains, packet of rich tea fingers .coat the biscuits in icing and let dc put sprinkles on, keeps my dd amused for hours.
make Oreo biscuit cakes, grind down a load of Oreo biscuits, melt a packet of marshmallows and some butter in the microwave and add in the crushed biscuits, pour into tray,bung in fridge. Get dc to stir and pour.
Dd loves glitter, smother a page of card with glue and let loose with glitter shaker, messy but keeps her amused for a while. Pound land do lots of crafty packs, paint , glue ,Pom poms etc get them all there. have made a sort of washing line with string where her masterpieces are pegged to show daddy her 'prettys' when he gets in, also lets them dry without her touching after I've cleaned up!
Also I often get one of those Betty Crocker pancake shakers, add water get dd to shake (whilst sat in high chair) I will cook one round , while they are cooling ready to eat ,do the next round, lovely and quick to do. We always have them when we've been out in the cold!
Dd has a 'proper' water table now, but before I bought it I used to fill a washing up pan with warm water and bubble bath lay down lots of towels and throw in her ducks from the bath, stacking cups, kitchen jug anything to splash about.
Do you have a Pinterest account op, there are lots of fab ideas on there, I have a board ready for wet weather ideas!