Do we have any obligations to our Marriage Celebrant once we have organised our wedding with him/her?

You do have obligations to your Marriage Celebrant once he/she is engaged by you.  Most Marriage Celebrants will have you sign an Agreement which sets out these matters.   This Agreement is actually a contract between you and your chosen Marriage Celebrant.  A typical Agreement would include the following.

(a) The payment of the full amount of his/her fee by the required date which will, in all situations, be prior to your wedding. 

(b) Advising your Marriage Celebrant prior to making any change to the time of your wedding - as it is quite possible that your Marriage Celebrant may have another commitment at this new time and will be therefore unable to perform your ceremony at the new time.

(c) Advising your Marriage Celebrant of any change to the location of your marriage ceremony as soon as such a decision is made.  The same applies if you are planning an outdoors wedding.  In this case, however, your Marriage Celebrant - during the planning stages - will have enquired as to what contingency plans you have in place in the event of wet weather.  Nevertheless, you should never assume that your Marriage Celebrant can read your mind - so in the case of an 11th hour switch of venue owing to bad weather conditions or anything else, you must always contact your Marriage Celebrant, or have someone contact him/her on your behalf as soon as you make the decision to switch.  The onus for this rests with you.