Hey miamamma
There are 2 years between my 2, and since DS came along 4+ months ago, DD has wanted to be pushed everywhere in her buggy too, despite previously being happy to walk. I agree that there is a bit of regression/'working it out' for the toddler when a new baby comes along. My DD IS an active one, but she lacks in other ways (oh heck that's a rubbish way to put it, but ykwim!) such as talking - she's been a bit slower than her buddies, but her balance and confidence at physical stuff is excellent. She is all about free play though, like Creations said, the context definitely matters. DD loves running round the park but not necessarily doing things "properly" eg she'd much rather run up the slide than slide down it, and we had been going to Tumbletots - when we were in the youngest group it was more free play based, but in the mid-age group it is structured and she doesn't like it anymore - possibly the opposite to how your DD would find it? Likewise she hates the free library singing sessions because they're over crowded, but loves the EXACT same thing in a class that I now pay to attend which has lots of space.
It's hard to not worry though, I get that. I'm always thinking I wish she'd talk more or I wish this or that, I have to keep telling myself to stop it! They do get there eventually, I'm sure we won't bat an eyelid when our second babies face the same hurdles.
xx
ps mermaids in trees is very funny!! My DD probably doesn't know what a mermaid is cos she hardly ever sits still long enough to read a flippin book! ;o)