I’ve battled this for years, I’m in my fifties.
I was the only one who didn’t fill the party bag with crap plastic, a piece of cake and a balloon each child got. So many mums told me they were in awe of me, well I didn’t have the money but my dc had fun parties and still talks about them now.
Flower pots, I cut the bottom off milk cartoons and make into pots, mainly for growing things to go in garden later or to the allotment.
I tie a huge floaty scarf round a huge sun hat, instant personal tent, ok probably doesn’t work with a child. Use a sheet, tie/peg it to a deckchair /pushchair and pull towards to make a space, instant tent.
Get crafty, save ribbons, string etc from wrappings and make decorations. There’s lots of inspiration on things like Pinterest.
Then with what you’ve saved buy a decent chopping board perhaps so that it lasts and lasts and you save the money on buying lots over the years, all aids helping our children’s future on this planet.
I’ve given up selling things. I seem to be jinxed, if I ever do get interest it’s always a hoax buyer or someone who want to cause me lots of agro. So I just donate to my local charity shop. I have however bought lots of Facebook market place, mainly toys for my grandchildren and equipment for having them here and it’s worked fine. I think sometimes there’s just too much of the same stuff out there, if you are in need of it then you get a good choice, selling well that’s a different matter.
Enjoy your trip to the beach.