Please be careful with your little one though. I spent the whole evening in A&E last night due to a little one getting too close to a bat while it was being used in a game of swingball. Unfortunately because of the delay in the hospital treating him he will have a lifelong scar because of it.
I'm sorry to hear about your little one Janis. I hope he's not too sore and recovers soon. Maybe I would be safer with the football swingball. I have been looking at those too. But they seem expensive for what they are.
We have the one that you spike into the ground, small and works really well - lives in the garden and doesn't kill a patch of grass. The box ones are not as study, okay for kids I guess though.
We have the one with the base you fill, and even my 16 stone hubby hasn't managed to knock it over yet. I was giving it a good whack around with my 9yo the other week and it was fine. We used to have the screw in one, which was fine too, but it got left out and went rusty! I think it's psychological for us, having a box to put it away in means it actually goes away and doesn't end up propped by the side of the shed!
If I were to be choosing, I would go for a hammer in the ground type, even if just to avoid the extra journey to the tap to fill up the base and then to have to carry it back again to the pitch. You could use rock.... but then you've got to find and collect them. To simply hammer it in the ground would get my vote.