Don't hit anyone with too much if they're just getting into somrthing new. You're trying to achieve many things already (new ruleset, scale, time period, whatever). K.I.S.S. will never fail, but that doesn't mean the game has to be boring.
Another option is you loan out your collection to them, ie their 750 points and your 750 points of Germans gives you an opponent to your 1500 point French army.