Hi Sandra

I agree mostly with James' comments.  Below are a couple of other suggestions for you. 

Best of luck with the job application. 

I have a lot of experience with child care and education and also I have many artistic, experiential and creative activity resources for children.

I worked in the La Paz Hospital pediatrics plants with admitted children and their families and I also coordinated art therapy sessions for children and their families at risk of social exclusion.

In the education field I worked as a teacher of visual arts in different schools with kids between 3 and 11 years old.

...."Colour in Orphanages" programme in India. *

...I consider myself an affectionate, comprehensive and happy person who loves to work with...**

...really motivated to work in this field.***

* UK English

** I know you want to avoid using the same word too many times.  'to deal with' is not the right fit here though, in this context.  Perhaps....'help' as James suggested. 

***optional wording

Help with my cover letter

I have written this letter for my job search. Could somebody help me with this, please?

I am an art therapist specialised in the education field and I love children. I am writing to you in order to inform you that I am really interested in being part of your great team.
I have a lot of experience with child care and education and also I have many artistic, experiential and creative activities resources for children. I like to teach from experience and help the children learn via active listening, always with special attention to their needs.

As art therapist I have worked with children with Asperger's Syndrome and children diagnosed with Attention Deficit Hyperactivity Disorder. I worked in the "La Paz" Hospital pediatrics unit with admitted children and their families and also I coordinated art therapy sessions for children and their families at social exclusion risk.   social exclusion risk=no estoy seguro de esto, no lo he escuchado

In education field I worked as teacher of visual arts in different schools with kids between 3 and 11 years old. At the same time I coordinated different arts education programs aimed at children and I have participated for two consecutive years in the "Color in Orphanages"program  in India.

In addition to being a hard-worker, sociable and responsible person, I consider myself an affectionate, understanding and happy person who loves to deal with children. I love spending my time with them, because my vocation is to help children, and I am really motivated.