I once had this debate with myself about 2 commercial lambs orphaned at 5 weeks. In the end, I penned them in a shed with other sheep next to them, and we fought for 4 days with one and a week with the other to get them to take milk from a bottle. I then fed them in the pen until they reliably came to me for the bottle, which took another few days, and then let them run in a small paddock with their neighbours, giving them a bottle twice a day for another week and a half, then just one a day for another nearly 2 weeks. They did brilliantly, went off at the same time and with the same grades as their contemporaries who were reared on their mothers. They would almost certainly have taken many more months to finish, and possibly had issues over winter, had I left them to manage on grass and creep at that age. But if they had been 6 weeks or older, I would not have put them through the trauma of being penned and having to learn to take the bottle. They wouldn't have got off as soon or at the same grades, but we would all have been spared that very hard week.
Funnily enough, today is day 3 of teaching an orphaned Shetland x Manx to take a bottle. He was 30 days old as his mum died, and in tip-top shape at that point. We haven't had indoor / penned lambs for years, and although there is a triplet I could have removed to keep him company, and I have chosen instead to leave him running with the flock, and gather them in once a day, and see what I can get him to take. First day I had to do everything for him, yesterday he drank a little but hated me and hated being constrained. This morning I thought I might do better, as he was clearly hungry and trying to pinch off other ewes as they milled about. Sure enough, he lay quietly across my lap and drank about a hundred mil willingly, thank goodness, but it will be a few more days I think before he runs to me and I don't need to gather the whole group in to get hold of him. I will increase the amount per feed gradually, as he won't be used to a gutfull twice a day, but to little and often. And go to feeding him twice a day as soon as I don't have to bring the entire group in to feed him. At 30 days and in tremendous shape, I figured he could take a few days of little milk while we got this figured out together, and the benefits to him of being with his friends and aunties outweighed the alternative of more milk but a massive amount of constant stress.
So it's always a bit of a judgement call whether and how you do it, and many factors in the equation. But at 7 weeks and eating creep, personally I would leave them to it. The lack of additional stress will more than make up for what you might get into them if you tried
