http://www.hassandlass.org.uk/ shows for 2002 that there were ~320 cases of magnet injuries (nature unspecified) in home/leisure scenarios vs. ~12000 coin injuries.
However that doesn't help us much. Strong magnets are far more prevalent now and the specific toys that caused most injuries weren't around in the UK, I think (?), back then.
Moreover, that probably makes magnet injuries per item in the home massively outweigh coin injuries.
I looked for EU IDB stats too but didn't get anywhere, my starting source was http://www.rospa.com/resources/statistics/ which lists some other potential data sources at the bottom.
>How many kids are hospitalized/die from swallowing batteries?
For button batteries:
poison.org[1] lists 54 fatalities since 1977; the Children's Hospital of Philadelphia has a page [2] that mentions "Fifteen children have died — 11 of them within the last six years" but it isn't clear when exactly that page was published.
How many children are hospitalized/die from swallowing coins or lego?
Do we need warning labels on coins?
How many kids are hospitalized/die from swallowing batteries? I'd bet it's a lot more than magnets, and batteries can be pretty lethal.