With respect, any article written by the Daily Mail is going to be clickbait sensationalism. Murderous immigrants on every corner. Horrible site.
I've just come back from a few days in Dublin with my early teen kids. I live in the UK but went to uni in Dublin and from a small town about an hour away. We stayed out of town with extended family and drove in to do stuff. Used a car park just off the Northside quays. Bit smelly but not uncommon in public carparks.
I certainly didn't feel unsafe and spent a fair bit of time in effect training the kids to navigate around so they could be let loose on a future visit as my patience for H&M and other teen fashion destinations is limited. They are not savvy City kids but I would not be concerned for their safety beyond the usual don't wave your phone around and watch your wallet instructions they'd get on a day out in London.
The nice thing about Dublin is the "things to do" are concentrated for the most part within a square mile. You could [at a trot] do all the sites you're interested in, in a day
I would recommend
Museum of Modern Art
National Gallery - no need to book, just wander right in. Around the corner from Trinity
Kilkenny Store - Nassau st right beside Trinity. Some lovely things.
Trinity College obviously. Book tickets for the Book of Kells in advance
National Museum of Ireland - Kildare St location in the city centre for the Gold [Or] exhibition. The other site is more later Irish history which is interesting but I didn't think would grab the kids in the same way.
Did the Viking exhibition with the kids years ago. The most memorable thing about it was the smell [very realistic] and the lovely old building but then before people take offence, I was herding two small children.
Didn't bother with the Guinness storehouse or the Jameson whiskey place on the north bank as well, kids in tow and driving.
Can't recommend hotels as haven't stayed in one in 20 yrs.
Dart is basically a commuter train along the coast. Only reason to use it that I can imagine is if you'd like to go to Howth or Killiney for a Sunday lunch on a weekend away and maybe walk the pier at Dunlaoghaire for a bit of fresh air.
Things I would have done with a few more days. Driven or taken the train from Dublin to Belfast for a day trip. The Titanic museum is really, really good.
Gone to a GAA match at Croke Park, preferably hurling. Amazing atmosphere, unique experience
Go horse racing. There's usually a race on somewhere. Punchestown festival is coming up but there is horse racing on everywhere.
The EPIC museum.
With access to a car and not a lot of time - I'd get out of Dublin - head to Glendalough which is simply gorgeous.
Russborough House is also quite special and not a golf course in sight
https://www.russborough.ie/explore-learn/the-house-its-history/
With time I'd head for the West or the South West and spend little time in Dublin as it is lovely but ultimately a small city with limited things to do in comparison with London, Paris, NY, DC etc.
Things I would never do but might be of interest - cold sea swimming at Forty Foot made famous by Bad Sisters.