Me my wife and our three chilldren 16 months 3 and 9 will be going to Cornwell for the first two weeks of August. We have two tents, the first larger tent being our Sprayway Canyon 8+2 wich is polyester and has lots of space. The second being a Marechal Compact Luxe 4. Which is canvas, but is smaller.
I'm stuck on which one to take. I have never used the Marechal as we always took the larger sprayway. The three kids like to share one bedroom pod so we usually have more bedroom space than we need. So i am thinking the benefits of the smaller tent outway the larger tent.
I would go by the weather report nearer the time. In blazing heat you'll want the canvas, as it stays a bit cooler when it's warm (and conversely warmer when it's cool) and it's likely darker too so you'll be able to get the kids to sleep in hopefully.
If it's wet then take the bigger poly, as the space will come in to it's own when stuck indoors between rain showers.