Entertaining toddler and teenager

[Miss2188]

I have a 2 1/2yr old and 7m old (girls), and a 14yr old stepson. He's with us for 8 days over the next fortnight (4+4 separate stays). What sort of activities will entertain both toddler and teen, while having a baby (who will happily tag along anywhere in the sling)?

Up for outdoors and indoors activities on a budget. I thought camping, but my husband (maybe rightly so) thinks it'll be tough / stressful with 5 of us in the car with our stuff. I don't know what to suggest.
Please help x