Hi Tazz, this sort of interference with a site can cause problems besides those you mention yourself.

One of the biggest problems may be that of search engine ranking. Search engines can take some time parsing your site and ranking it. So removing content, even temporarily for a week, can drop your ranking and take time to re-rank after content is re-added.

As for a method of actually doing so in Xara, it would be to move the page content horizontally off the page and into the pasteboard area. Provided you have Web Options / Website / Clip to Pages Edges selected, nothing on the paste board is published with the site. You can then add temporary content to the page area saying "Under revision" plus contact details etc. Also remember you'll need to do this for all other pages on the site. So again perhaps a single page "menu" would better suit?

Then when the client gives you new content you can delete the temp content, move the old content back on page & amend as required. However bear in mind the SEO issues mentioned above. If your site ranks number one for "Shrimps in Peanut Butter" and you temporarily remove such content (i.e. to change the price) then reintroduce it after a week with an amended price, will the SE still rank it number one? It'd disappeared, how long will it take the SE to re-parse it?

Far better to explain this to your client, arrange a new menu launch date (online & in house) and do it on the same date.

Just my thoughts.