I just had a look at the Travis County Probate Court web site. Unfortunately, you can't be pro se, you must be represented by an attorney in this case. (You can be pro se if you are only representing your own interests. Since you would be seeking to represent the interests of someone else, you are not allowed to be pro se.)
So I would ask an attorney what they would charge to represent you for the initial filing and then the ongoing costs (for annual financial filings, etc.) until the child turns 18, and balance those costs against the costs of waiting (which not only includes potential taxes and penalties, but the opportunity cost of not being able to withdraw the money even if the child had a good reason).
Good luck.
https://www.traviscountytx.gov/probate/probate-forms
Court Policy Regarding Pro Se Applicants