@SkeeterUK that's not an especially common problem now, but there were a few instances around especially when FS19 was first released. Most were solved by updating graphics drivers, but I wouldn't expect a user here to have that issue.
DX10 while a workaround doesn't run nearly as well as DX11. You can try posting your log file (stick it in a spoiler tag as it can be quite long) and I'll take a look, but I doubt there's an obvious fix. The log can be found in
C:\Users\%username%\Documents\My Games\FarmingSimulator2019\log.txt
It's not an AMD-specific issue either. AMD hardware has always been second best performance wise in Farming Simulator, but they usually work perfectly well.
How would this suit a 5 year old? My son loves tractors and combine harvesters. I could set him up in the sitting room with it.
It's PEGI 3, so it's suitable. There's a bit of a learning curve for playing properly and maximising profits and things, but I doubt he'll care about that. The game is essentially a driving game, so he should be fine.
Don't install the Seasons mod for him. It's a brilliant mod, but it adds a fair bit more realism, micro-management and planning to the game, so probably not best for a young child.
Plenty of good British-themed maps around if you want the traffic on the correct side of the road and things too. Marwell Manor, Oakfield Farm (both real maps) and Greenwich Valley (fictional) are excellent British maps which can be downloaded from the in-game ModHub. None of them work well with the "build your own farm" feature, so if that's something he'll want it's best to stick to one of the default maps.