How do I transition from adult/elder rehabilitation to pediatric outpatient care?

Brush up on peds, everything you do is weight based, it's a totally different world. Learn accessing ports, central lines, starting 24 g ivs
Obtain PALS and of you can take a course in peds.

I would suggest speaking with a local pediatric outpatient center, whether it be a clinic or office. Speak with the unit/office manager and ask if you can set up a day to shadow. Most inpatient hospitals are willing to work with potential employees, I would assume that it would be the same in outpatient settings as well. If you have a friend in the field of interest, ask them to speak on your behalf. Nurses change fields all the time and I believe most facilities are willing to speak with you if you show a sincere interest and dedication to the field.