We are (2adults/2children(7yr/10month) arriving on Saturday 30th to Paris. What is best ticket to see paris central and around on 30th April. Then on 1st May visit to disneyland, stay there. Then best Ticket to return back on 3rd from Disney to paris and See paris Central.
For visiting central Paris I'd recommend buying a Ticket Mobilis day ticket 1-2 zone for each adult, Ticket Jeunes week-end 1-3 zone (no 2 zone option) for 7-year old, no ticket for 10 month old (under 4 is free).
To get to Disneyland from central Paris, single RER tickets good for Marne La Vallee station (ticket window at any Metro or RER station can help you buy the right ticket) for 2 adults and 1 child (at child rate). No ticket for 10 month old. You'll buy & use a similar ticket for return. You can purchase those at the same time; They don't expire.
To see central Paris after returning from Disneyland, repeat the same Ticket Mobilis / Ticket Jeunes week-end purchases.