We're due to leave on Monday for our ten-day break at a holiday park in Tuscany. But - the forecasts are predicting daily temperatures of 36 -38 C throughout the next fortnight. 
(much hotter than the average temperature there at this time of year, which I checked before booking).
We've kitted ourselves out as far as possible for the heat, but are still worried about it spoiling the holiday. We had planned to go on some day trips, but are worried that with temperatures that high, it'll be unpleasant to be outdoors. So we could be stuck in our mobile home most of the time (mobile home is air-conditioned but fairly small.) I'm worried we'll end up irritable / sunburnt / getting heat stroke.
DH has even raised the idea of cancelling the holiday. (We wouldn't get any money back at such short notice.)
Other information: we are flying there, we've arranged a hire car. The DDs are 12 and 10.
So, are we being unreasonable to worry / consider cancelling? Would those temperatures spoil the holiday? If you've been on a family holiday in similar temperatures, how did you fare?