Don't worry about it. My son (now 27 months) was the same. (Except he had no interest in balls and didn't do much more than walk somewhat fast at 18 months!) What I learned is that he's just very social and cautious. This is somewhat frustrating in the park. For example, he observes the big kids talking and playing around him rather than playing himslef for the first 20 minutes or so after we arrive. Nothing like standing around on the playground while all the other moms chase after their kids! When he starts playing, I have to encourage him a lot. It takes about 5 minutes of persuasion to get him up the slide, as he slowly climbs (or sometimes even crawls) up the steps to it! Then he has figured out how to use his feet to make himself go down the slide extremely slowly which makes me nuts. There will be tons of kids going past him as he climbs up and tons waiting behind him as he slides down. I used to worry that people would think there was something wrong with him, or that he would gain too much weight because he's not very physically active. Neither happened.
On the other hand, when we get home, he will "pretend" and repeat entire conversations that he overheard from the big kids in the park. It's crazy how much he observes and immitates. Not to brag, but he is by far the best talker (boy or girl) among the toddlers we play with. I routinely get together with a friend who has a 4 year old girl, just so he has someone to play with and pretend with on his speaking level. He has learned his colors, numbers, letters and shapes now pretty easliy. He loves listening to people talk and sing, and loves to sit and have books read to him. He also plays with cars and trucks, but they've always had personalities and "talked" to each other when he plays. And when he's not doing those things, he's talking non-stop! I had to just accept that that's what he's focussed on and be proud of him for it.
I think this month my son is finally starting to be more interested in physical things. He doesn't want to sit and read as much, and he's sleeping a lot less and is less of a chatterbox. On the other hand, he is actually getting off the floor when he jumps! He also climbed up on our bed by himself for the first time this morning. He's being more of a little boy- breaking through the safety locks on the doors, getting more adventurous on the playground, and generally being more mischevious!
Anyway, my conclusion is that they'll all learn skills in their own good time. They'll focus on what they want to, regardless of what we do. Hopefully our boys will start getting interested in crayons before they hit school, right?