My DD1 is 5 and has never been a sporty kind of child. She's quite uncoordinated, struggles with stuff like riding a bike, we are going to swimming lessons with a 1:2 ratio and it's clear how far off the other kids she is, it's like she can't do two things at the same time, or like she can't process how to kick her legs as well as be floating. She is coming on but very very slowly, and I find it really upsetting (I don't show it to her) watching the gap between her and other kids widen when it comes to being physical. Stuff like climbing as well she's pretty poor at.
To give another example, she took ages to learn how to balance her weight on a swing properly to stop herself just slipping off. To me it seemed like such a natural just kind of thing to move your body weight so you don't fall off, but she couldn't balance that way. Even now she's very precarious. She also can't jump onto swings like her pals, I still have to lift her if it's too high. Never got the hang of a balance bike.
She was always kind of on the later end with gross motor milestones, still within range but near the end age rather than start. Her younger sibling is totally different and I would say almost more physically able in some ways already despite the 3-year age gap.
She's active enough, we walk to school and back every day which is about 15 mins each way, she rides her scooter (she can manage the 3-wheel one) and likes running and dancing, the trampoline, she goes for long walks with her dad at weekends, she has two PE days at school a week.
She's incredibly crafty and creative, interested in languages, singing, she's a very healthy child, rarely ill, doing fine at school, fine at home although she has her moments as all 5yos do!
At what point do I stop trying to push her to do this stuff and just accept that it's not for her? We keep trying the bike as so many of her pals are out and about on them, but she has very little interest in the first place. But then I feel we are doing her a disservice by not having her keep up with her friends. She was invited to a bike party over the summer and had to take her scooter because she can't ride her bike, and then just got left behind as she was a lot slower.
Swimming I know is a 'life skill' so we shall persevere with it but the progress is glacial because she just seems so uncoordinated and unaware.
I feel awful because I feel myself getting so frustrated 
I wasn't a sporty kid myself but I learned to ride a bike etc at the 'usual' age without any real problems.
Has anyone else had this issue or has any insight?