No one can describe how hard it is to go from being used to doing your own thing to having someone you need to be with and respond to at all times. Before any of the other stuff associated with adoption, I found having another person (or two) with me 24/7 just overwhelming.
Routine and structure is important, for you and them - for me knowing they’d both be in bed and sleeping by 7.30 got me through tea time. Your sanity is more important though, and you are very very early days yet so do what works for you and them. Everybody fed, nobody dead was my mantra for long enough, just cover the basics.
I know this could be a double edged sword but can your social worker help with some respite, either with a supported nursery place or some such? At this point I was seeing my social worker and the kids social worker weekly and tbh they were both a fantastic support letting me cry if I needed to, they had some very helpful advice for me and my DH and in time (ie after about 5 weeks) fully supported my DC starting school and nursery - if fact they both suggested it. I don’t know what your relationship with SW is like but they can be fantastic post placement.
It also might be worth checking with the foster carers whether they had to sit with your toddler at bedtime, how they would settle him etc and how he was when he first went to foster care cos there’s a good chance he’ll have regressed.
Sending you so many good wishes, hang in there - you’re doing great!