you've stated where you will be hiking with the "wee bairns" (as the Scots say). good. i'm not from that area, but many posters have, in the past, posted links to fairly authoritative articles on wilderness water quality for that area. perhaps a 'Search' of the Forums or the Forum Index will yield some fruit and shed some light on your question.
are you talking practical here? or, theoretical?
since your children are involved, are you attempting to eliminate any theoretically possible biological agent?
depending upon your reply to these questions, will determine your course of action. if you prefer (other Forum readers will undoubtedly prefer that you do), you may email me at either email@example.com or firstname.lastname@example.org and i will reply with suggestions. i will attempt to keep the answer of moderate length - maybe the equivalent of 1/2 page to full page (if it were printed out). i won't go into details on the "bugs" (unless you specifically request it), but will explain generally what you can expect from each type of purification process and what might make it past any single method of water purification. this would largely be theoretical. it would be practical only if hiking in an area that might have highly contaminated water. from what i've read, your water out there seems to be much cleaner than some parts back here in the northeast.
not a problem if you care not to email me. the Forums have several times dealt with this topic in nauseating detail (mainly, courtesy of this poster).
enjoy the treks with your kids. used to love doing that; good memories.
remember, if, for any reason you adopt the prev. respondents gravity filter recommendations (good recommendations IMHO), and if after filtering you want to eliminate viruses and anything else that might make it past the filter (depends on filter pore size), but prefer not to use chemicals because of the young children (check with their pediatrician on the advisability of the chems available), a UV-C sterilization product can be utilized. the new AquaStarPlus is now "unbreakable" and does not need to be carried in the included Lexan bottle. its approx. wt. is a tad (the universal standard "tad" is meant here) over 3oz. - including batteries (i've read that on their website, but haven't weighed it myself). I've spoken with Meridian Design (mfr's of AquaStarPlus) and they assure me that other than a hard fall on an unpadded unit, it will not break when outside the bottle - even though it still looks fragile. you can throw it to the ground (a flat, hard surface) & it will "bounce", not break.
[note: as far as UV goes: since i'm not familiar with how sharply the light wavelength "cut-off" is of the generating units. i don't recommend looking at the tube when it is generating UV. if it produces only UV-C wavelength, then most (or possibly even all) of the UV-C will not make it through glass or plastic. however, if the tube does not have a sharp "cut-off" and some longer wavelength UV light is also emitted, some of this can pass through glass and plastic. this may be an unecessary precaution. i only suggest it since i am not familiar with the precise specs of the light generating tubes used in the various products available for our application.]
hope this info helps.