Bad luck losing the ewe
If the lambs had already been eating creep before they lost their mum, I'd have said that at 7 weeks they'd be fine so long as they eat at least 1/2lb creep each per day. But the worry is that they will lose a lot of condition while they get the hang of eating creep.
I would keep trying to get them drinking from a bottle, they may just suddenly switch onto it as they get hungry enough. I'd also try raw (straight from the cow) cow's milk - which is easy for me as we have our own Jerseys, and an organic dairy farm as neighbours, too. I sometimes find that older lambs take to cow's milk more readily than the replacement ewes' milk. You could also try putting some milk (either cow's or the replacement ewes' milk, or a mix of both) in a bowl to see if they'll lap it.
Modified to mention that if you can source raw goat's milk, that would equally be worth a try.
Older farmers around here talk about 'milk pellets', which were so like solid milk the lambs took to it right away. I've no idea if there's any such thing available now - but maybe someone else does?