I couldn't find anything in the TOS with regards to their search button, and getting yourself banned (accidentally). My site is under construction right now and have images of ads in places where the ads will be, once i go live. can i add the code for the google search bar on my site? i have an image of it there now. will having the code there start my impressions counter and potentially cause an issue? what about searching for things (to see what the results look like when searching my site)? am i allowed to click on the results google returns when searching my site? im not even going to ask if searching for things and clicking on the results that take me to other sites...
As far as I know, you're allowed to use the Google search bar within your site so long as you don't click on the sponsored results. There is no issue with putting the search bar up now, even if the site is still under construction. Impressions will be counted but you won't be credited for them.