Hi Cherikey,
Oh, your holiday sounds great!! The last time we went to the coast the whether was misrable too!
I found this really cool website that has really "easy" but really creative ideas. There will be a few ideas with very basic ingredients that you would have to pack, like maybe straws, bicarbonate of soda, vingar, shaving cream, food colourants.
Check out the activity with the milk, dishwashing liquid, food colourants: it is magic!
Take craft glue and scissors, you will be able to make collages with leaves, twigs and other organic found objects.
the pretend cooking activity is also great, pack some dried beans, lentils, rice etc.
I have recently given my 3,5 year old a grater to start grating and she is doing really well! It keeps them busy for a while. He have only had on minor cut so far.
Here is my new favourite website:
www.playcreateexplore.com/p/activites-for-ages-1-3.html
ps: activities start from younger to older, scroll a bit down to 3 year old...However some of the younger activities (like the "clean mush") will also be fun!