Have you read the depakote lawsuits? I did a quick google search and the biggies seem to be:
1) use of depakote during pregnancy resulting in birth defects. obviously.... not an issue for your son, unless he also has a uterus, which you may not have mentioned, I guess.
2) the Arkansas lawsuit, where off-label depakote was marketed and used for non-epilepsy related conditions (schizophrenia, etc) which was technically a false advertising lawsuit.... not a reason to not use depakote for it's actual intended purpose (to reduce seizure in epileptic patients).
Aside from that, most of the side effects seem to be gastro-intestinal.
If my daughter needed and was prescribed depakote (just based on the info I found in the last 5 min) I would have no reservations about using that medication.
I was prescribed Lamictal (lamotrigine), which is commonly used to treat seizures. I had absolutely NO side effects (and actually didn't find that the medication was helpful to me, so I stopped taking it). But, the biggest side effect from that was a rash, which they said was most common if you don't "ramp up" and instead just start at a high dose. Oh, well, I just googled that..... and apparently the FDA has found a link between lamictal and aseptic meningitis. So, I wouldn't do that.
I hope you find something that works for your son. Good Luck.
*also - as far as daycare or pre-school, I would maybe look for a nanny. I'm not sure what your needs are as far as timing / hours / financial etc, but I used sittercity and care.com and on both sites you will see lots of care givers who have experience with *special needs*, but aren't THAT expensive.... (although you'll also find RNs who are quite expensive).
The sitter I used for my daughter grew up with a brother with muscular dystrophy and had also nannied for a boy with cerbal palsy. (she found my then 8 year old daughter with her contstant but random girlie-pre-tween-hystrionics, nail polish needs and contstant hair-braiding demands a piece of cake, by comparison).
I would guess your son would be a *special need* and you might even find someone who has cared for a child with epilepsy before, which would be an additional resource for your family.