So let me start by saying that this might not be the trip you'd wish to go with small kids or really anyone who likes to travel in comfort: to enjoy it at the fullest you WILL need to do it on an ebike (that's more like a small scooter, not those electric-assisted bikes) as they are sometimes the only (or at least the easiest) way to get to the more off-the-beaten-path pagodas. It is HOT out there and most of the roads outside the city walls are unpaved, so they will get dusty or drenched depending on the weather.
Bottom line: it is supposed to be an ADVENTURE, not a leisure stroll around the countryside. If your kids are up to it, definitely bring them along, but otherwise maybe reschedule this for when they are a little older (or go before having any, that would also work). But, hey, its gonna be SO MUCH FUN, that I promise you.
Sunrises and sunsets are the crowdest time to be in the major pagodas so either go for the smallest, off-the-track ones or be prepared to see it with a crowd.
Be aware though that as many places in SE Asia, locals are everywhere trying to sell you their stuff and they are VERY annoying (although some of them sell some beautiful paintings).
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