In paris 1 month from oct 15, at least one SNCF RT to Lille then Uber to Hem) and multiple ile de france and paris trips, all agrd over 60 ... best bet please for a multiple service discount deal? And purchase in advance if possible so we could use arriving at CDG ... and we speak and write French ... Mille fois merci 🥰
Unfortunately arriving mid-month makes the Navigo with a month pass not worthwhile (since it's validity period is strictly from beginning of month to end of month, not for arbitrary 30/31 day stretches).
The Navigo week pass may be your best choice if you plan on using public transportation inside Paris and around Ile-de-France often (say, at least 4 one-way Metro rides per day or 2 one-way RER/Transilien rides per day during the week, Monday through Sunday).
There are no discounts on passes for non-residents, regardless of age. (Only residents are eligible for discounts on long-length transit passes.)
Navigo passes aren't sold abroad nor delivered, only purchased in-person at ticket windows or offices within Ile-de-France. There is a 3rd party ticket reseller who can mail Paris Visite tickets which are multi-day, multi-zone paper tickets (up to 5 days in duration). But, note that these are more expensive than the Navigo passes, require a handling & delivery fee, yet offer no additional transit benefits save for coverage of OrlyVal train from Orly Airport) and are aimed at tourists.
Also, Lille is outside the area of coverage for any Ile-de-France travel passes or tickets. You would be need tickets issued by SNCF or its subsidiary branded services for traveling to Lille.