I think my kids got food poisoning

It’s my sister in law’s birthday this week amd we celebrated today, a few days in advance. There was a cake which was made thursday (it said so on the packaging) and both my youngest kids (ages 4 and 2) had some around 3 pm, it’s now 1 am and both of them have been going to the bathroom every hour or so (my youngest is still in diapers though) and their poop is dark green (the frosting on the cake was blue). They are both complaining of a bad stomachache on top of that.

Is there anything I can do at all? Something I can give them?