Due to the strikes, I've been having trouble navigating around Paris with bus and trains being overly crowded and untimely. But I understand situation but I want to plan a good trip for my family and I have a few young kids to handle as well. Please advise
If you are making the trip from Paris Simplon - Val d'Europe between 6:30 a.m. - 9:30 a.m. or 4:30 - 7 p.m. during weekdays the most direct route would be to start at Simplon station - Metro 4 in direction Mairie de Montrouge until Chatelet, transfer to RER A direction Marne la Vallee until Val d'Europe.
Outside of those hours on the weekday, during the Paris train strikes, it's not possible using Paris city public transport. The only alternative I could suggest is taking Metro line 1 to the eastern edge of Paris, Chateau de Vincennes station, then taking an Uber to Val d'Europe.