not sure for solen since i haven't attended the festival. there was some concerns last year about overcrowding but i think they were sorted throughout the festival.
i've attended oya last year and it was by far the most family friendly festival i've ever been to.
the organization was flawless. no overcrowding, plenty of space to watch the shows, even on the main stage. there was also two tents for childrens where they could find some activities to fill the time between the concerts. people were friendly and helpfull and everything went smoothly.
also a great plus is that the festival is in the city and you have plenty of public transport that you can you to go home quickly and smoothly after the concerts.
i would recomend oya 1000%.