This happened to me last March, the boys were 1.75 and 3.75 years old.
Fortunately they were in nursery for 4 of the 8 days. I agree with things said above:
Plan and prepare meals so you can just cook pasta and put the sauce you made last night on, heat something up, make an omelette. Ours get hungry all of a sudden and if you can't get them something quick then they drive you mad asking for bread, biscuits etc.
Walk in woods
Bus ride into town/to a new park
go to park
Picnic - kids don't care if its cold and muddy
Painting (proper messy painting)
make things - space ship is good, then paint it. Make masks
birthday list - get a catalogue (Argos etc) and get them to cut out what they want and stick it to a piece of paper
Don't feel guilty about sticking a DVD on especially in the late afternoon if you've been out
Dressing up, face painting
You'll be knackered but you'll all love it, it really helps with bonding!