Seizures brought about by stress are more related to panic attacks than seizures caused by abnormal discharges of electrical activity in the brain.
Taking medications (including anti-anxiety medications) on schedule are very important, but other things usually suggested for epilepsy to lower the seizure threashold - such as, avoiding dehydration and avoiding sleep deprivation - typically don't help for stress related seizures.
If you have not looked at the WDW
DAS thread near the top of this board, I would suggest checking out post 1 of that thread. (There is a similar thread for DL).
Kind of in a nutshell - (Disability Access Service) DAS allows guests to get a Return Time for an attraction. Any time after that Return Time has passed, the DAS can be used to enter that attraction. There can only be one unused DAS Return Time at a time.
In most cases, when returning, you would enter thru the Fastpass line, which would still mean a wait time of 5-20 minutes (some people have been reporting occasional longer waits).
Guests can also use Disney's Fastpass system in the same way as other guests.
DAS is designed to be used with Fastpass, so works best when they are used together.
To obtain a DAS, guests need to explain their needs/issues related to waiting in the regular (Standby Line). It is important to explain needs, not diagnosis.
Even with using DAS, you will need to be prepared for crowds, crowded places as the other posters mentioned. All of the things they suggested are things I would also highly recommend.
DAS only provides assistance for lines; you will still experience crowds, confined spaces and other possible anxiety provoking situations.
I would suggest looking at post 22 and post 27 on page 2 of the disABILITIES FAQs thread (located near the top of this board or follow the link in my signature). Post 22 is about attractions where guests need to stand for a period of time. Post 27 is about attractions where posters gave experienced claustrophobic feelings - many are part of the attraction itself, not in the lines getting into the attraction. DAS won't do anything to assist with the attraction related parts, so you will need to prepare for that.