Our French exchange student spoke very little English.
He ate very well, everything we offered him. Loved all things chocolate (hot chocolate, Nutella, coco pops etc.) I made huge packed lunches (baquettes with ham & cheese) fruit, crisps, biscuits, sausage rolls and more chocolate!
Roast dinner,Fish & chips ,Full English breakfast were all on his list of things to try.
The only thing he didn't eat was a pork pie in his lunch (fair enough) my DS said French boy and his friends found said pork pie hilarious and threw it around the school bud laughing 
I would have some French movies or subtitled tv available, also iPad so they can watch French iTube etc. They do need some down time as they have very busy and exhausting schedules. And yes to wifi password so they can stay in touch with family.
He didn't seem to shower much, or change clothes, but I just left him to it and didn't nag.
His family sent over some local Delicacies for our family to try, and I sent back some too (English tea in a fancy tin, Union Jack mug and some Scottish shortbread)
It was a very positive experience and my DS French went Up a grade. Enjoy and good luck