Cycling with one child in front and one on the back, having my dog running next to me on a lead, while pulling a trailer with my weekly shopping and talking to my Mum on the phone - is that allowed in Holland? Yes. It might not be safe, but it isn’t illegal.
Most road signs for cyclists that are used in Holland are universal and need no further explanation. However, some road signs for cyclists are specific to Holland, or might be used differently from what you're used to.