The valuation should be related to the actual moneymaking performance of the site (for which you presumably have records) & its potential performance. The same applies to the intellectual property. You really do need some professional advice on this.
Incidentally, do remember that if the site & intellectual property were wholly or partly owned by your husband, any proceeds from selling them will be part of his estate for probate purposes (unless they have already been valued & included in a probate application).