Mountain bike hire in late August

Hi, We are travelling to Campitello di Fassa in late August, we need to hire mountain bikes for around 5 days (childrens (aged 14 and 11) and adults bikes). Would you advise booking beforehand or is there plentiful supply? Is there anywhere you would recommend for the hire? There are lots of hire companies that have lots of info about their ski stuff, but no info on bikes.

Thanks in advance