This is really a very specialized issue for you.

I don't have experience with children this young using Valium. The only experience I have is with children using it rectally for severe seizures.

In adults withdrawal from benzos like Valium take a LONG time. They are withdrawn over months as a rule.

I also know that with newborns, or infants, born with addictions to opiates, they sometimes put them into a coma, and withdraw them in a special way with medical support. But I cannot extrapolate this to a toddler. I just don't have
that experience.

I went on PubMed looking for papers on this subject. Sometimes an email is
included with the paper, so one can contact the author.
I am not having alot of success with this.
This is the only one I found so far:

http://www.ncbi.nlm.nih.gov/pubmed/15567675?ordinalpos=1&itool=EntrezSystem2.PEntrez. Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.P ubmed_Discovery_RA&linkpos=3&log$=relatedarticles& logdbfrom=pubmed

Valium and other benzos lower the seizure threshold. So if you withdraw too quickly you may see a seizure. The jerks you see are perhaps myoclonus.
This one has an email too:

http://www.ncbi.nlm.nih.gov/pubmed/17541548?ordinalpos=1&itool=EntrezSystem2.PEntrez. Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.P ubmed_Discovery_RA&linkpos=5&log$=relatedarticles& logdbfrom=pubmed

This one gives time frames:

http://www.ncbi.nlm.nih.gov/pubmed/15907670?ordinalpos=1&itool=EntrezSystem2.PEntrez. Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.P ubmed_Discovery_RA&linkpos=5&log$=relatedarticles& logdbfrom=pubmed

My impression is that this is not common..so it is going to be difficult to
find a good answer.

P.S. I don't know why these links didn't turn blue for quick linking... you'll have to cut/paste them I'm afraid.