Hi Jo and welcome to WaB.
Well done for rescuing both baby hedgehogs. Your mum was right, hoggies in daylight are not a good sign. They are very small at 100g and they need help. Either something happened to their mum or most likely she kicked them out of the nest and they were struggling to feed for themselves, hence being in daylight.
The accomodation you've made for them seems good, just make sure they can move out of the heating pad in case they get too warm. It's a good sign that they are eating and drinking (and soon they will be pooping a lot too!).
Cat biscuits are good to keep their teeth clean; chicken flavour are the best bet. Some hoggies prefer wet food though, so try to buy both. Mealworms are a good idea too.
As they are quite small, they will probably need to be overwintered as they might not reach the ideal weight and learn the essential skills to survive in the wild before the winter.
If you can't keep them, you can try to find a
carer from the British Hedgehog Preservation Society.
You can find more information on rescued hedgehogs
in this link. Or in the
BHPS website.
Keep us posted and let us know if you need any help, ok?
Marcia