Make sure the awning you order is the same or similar length to your awning rail... Also worth looking at options based on what you think you may need, will one of the kids sleep in it when they are older. We look sat loads of options and went for a Vango Kela in the end as it just fits a bedroom if we need but isn't too big, can also put it up in about 10 minutes.
Look at ridgemonkey pans, they are epic, loads of videos on line, but go for the XL if you do. Stops splash and smells from the cooker in the van.
We've also bought a small double memory foam mattress from Argos, cut to size / shape with a bread knife and put a single duver cover over as a sheet and fits prefectly on the bed. All in cost under £40.