With turkey Mince you can still fall foul of the 5% fat or less rule.
(yes I am aware of the pun there

)
What I find is that if you struggle to find enough cheaper lean mince which qualifies, pad the meal or batch cook out with Quorn Mince.
It doesn't have to be 100% but if you keep it to be about 50/50 or even 75% Quorn and 25% meat, people tend not to notice because you still have the flavour from the actual meat in the dish and Quorn actually absorbs the flavours it is surrounded by (like Quark does).
Quorn mince is generally cheaper than 5% mince or any other to be honest, I find it regularly on offer for £1 for a packet, I think it comes in black tubs of 450g or 500g so you can cut costs down a bit too.
Don't tell your fussy eaters that you have incorporated Quorn into the meal and take note of whether they notice. If they don't, you have a strategy on saving money and reducing the hassle you have in finding enough lean mince.
Beware though, anyone with a mushroom allergy may be allergic to Quorn as it is made from a fungal matter, like mushrooms.