I would probably avoid wasabi. It's normal for parents in Japan to ask for sushi without wasabi for their children below probably around 10 when eating at sushi restaurants and I guess they would be used to handling children/wasabi combination so they'd probably know whether it's a good idea or not (probably isn't).

Admittedly it's unlikely that beef and wasabi would be as hot as wasabi in sushi but it's probably better to err on the side of caution.

However, is your child OK with ginger? Some children don't like it either, finding it a bit too 'hot'. Scallion should be OK - that's not hot.

Is there an option to order a child meal? With those two dishes you may end up with a hungry child, so a child meal (if it's on offer on JL) may be a safer option.

As for those who say that children should eat anything that's presented to them, hot dishes are a quite different matter from getting them to eat carrots, broccoli etc! I wouldn't give a young-ish child a vindaloo dish or wasabi peas and expect them to eat it. Wasabi and vindaloo can be incredibly hot and it would make things rather miserable for them (and in case you're wondering if I'm an over-protective parent, I don't have children, and my parents brought me up to eat anything put in front of them, but not potentially very hot food - I voluntarily started eating them and rather fond of them though).