For Carer's Allowance, if the granddaughter (I'm assuming she's a child under 16) receives either the middle or high rate of the care component of DLA, and no one else claims Carer's Allowance for her already, then yes, you could claim.
Only thing to watch for is that there is an earnings threshold of 116.00/week so if your payments from family and any other work you do are formal payments and exceed this your earnings may be over.
As regards free school meals, Carer's Allowance isn't a qualifying benefit, but if you get any of the benefits below you should qualify - if you don't get them - do you know the reason why? Maybe we can explain more...
Hope this helps