Hello, sorry you've not had many replies. I live on the island, have done for four years, I love it here but it's not for everyone. This might be too late to be of any use, but here goes anyway, just in case
There are mums & tots groups around, but you have to ask someone "in the know" to find them, it seems the island hasn't really embraced the internet at times. I found one group when I searched the internet, but having talked to other mums and childmiinders, there are actually quite a few.
Douglas is busy by Isle of Man standards, but not by London standards There are shops like Next, River Island, M&S, Boots, but only small branches. There is one Tesco but plenty of smaller Co-Ops and things. There are plenty of pubs and a few clubs but that's not really my thing so can't tell you much about those.
Like I said, I love living on the island, it's quiet and unhurried, and very beautiful. But if you are a city-loving person you might not like it so much.