So much of care: how can we make it long lasting habit?

My daughter, 18-month old, is willing to take care of others a lot these days. It's a such a big difference from my elder son.

She likes to trim our lovely dog, Halu. Even though she can't do it well, such a willingness to do something for others is really girly to us.

My son has been so naughty and active but I couldn't see such attitudes (of course there was around age of 1 and 2 but not this much extent).

She takes you clothes, shoes, phone and other things you used to carry and put on and ask you to take it even though you don't need it.

How can we encourage her to keep it up!?