@Kendodd you could try an online search for 'ceasefire march [place name]' or similar, which should bring up relevant local results including Facebook pages and should also bring up websites for bigger organisations coordinating marches or events - most of them have 'get involved' or 'contact us' options, which can direct you towards local organisers.
Local organisers are probably more helpful than general information from a 'central office', as local organisers can tell you about the culture of their own area's events - they might even be able to suggest some to avoid if you have particular concerns (eg, if the atrocities of 7/10 had happened in the UK, I might not want to go to an academic discussion about the technicalities of armed resistance vs terrorism given that it would have been 6 months since those atrocities and it would probably still be too raw - those discussions are important but can be distressing). Some events might also have 'buddy' options, where you could meet someone to attend with them - it can feel intimidating going to unfamiliar, politically charged environments.
Together for Humanity have done interfaith work advocating for peace, so could be one to check out. Parents for Palestine do some family events and organise 'children's blocs' for marches and demonstrations, so they could probably direct you to lead organisers as well as tell you about their own activities. (Disclaimer: mentioning these should not be taken as support or otherwise - they're simply being mentioned as options for finding out the information you'd want in order to decide whether to attend an event).
Another thing to remember is that, as many events are public, you don't have to be a participant to observe what it's like. You can just be in the area as an inconspicuous member of the public and get an idea of whether you would want to try participating. For example, if you see a march where people protesting peacefully, not doing upsetting things or behaving violently, that's very different from one where there's hate and threats.