I think who a french match for one of the children of James is inevitable and so I do not think likely a match between Mary and William of Orange:So, here’s what I’ve decided, James and Anne will become king and queen in 1685,following Charles II death. Mary will marry William of Orange, Charles duke of Cambridge will marry Sophainchslotte of Hanover.
Suggestions for the other kids would be most welcome
Charles will likely marry Sophia Charlotte of Hannover but James will push for a match between Mary and the Grand Dauphin (aka Louis XIV's son) like OTL: Charles II refuted that match and married her to William of Orange because she was the heiress presuntive but here Mary has three brothers. I think who Charles can tell to James who Mary's french match will be fine only if balanced by a protestant match for little Charles.
William of Orange can marry either Elisabeth Charlotte of Palatinate (who OTL was interested in marrying him) or another princess or wait another couple of years for Anne