Lugano is very child friendly.
It has that nice blend of Swiss and italian, and the italians are renowned for being child friendly.especially noticeable in hotels restaurants and cafes, nothing is too much trouble for them when it comes to children.
Ciani Park at one end of the promenade is graet and has lots of play facilities.
Swiss Minatur as you correctly mentioned.
Boat trips on the lake with the big passenger boats, plus....
You can rent small motor boats on the promenade and pedalos , both suitable for carrying adults and kids.
Then there is monte Tamaro, easy to find their website, which is a treasure trove for kids, so many things for them that impossible to list here.
All of the promenade along the lake edge has a wonderful wide pathway, safe from the traffic for walking / strolling with children
All of the shopping ,cafe restaurant areas just back form the lake are pedestrianised which is a safe and relaxing with young children.
Hope this helps.