I've been having a think about this
It seems to me that weaning isn't really your biggest hurdle here. Are you certain you want another so soon and can you convince your DH? If you're deadset for it and believe that starting immediately will give you your best chance, then teh weaning becomes a bit of a no-brainer. (if that makes sense?)
After DS I agonised for a bit about when to start again, remembering how long it took first time (though only 2 IVF cycles). In the end one thing made my mind up - I could not cope with babies close together in age.