There's absolutely nothing for your to be conerned about or worry about.
Those tax credits are specifically covered by UKBA and here's what they state:-
Here's the key part is .....for tax credits purposes, neither are treated as being subject to immigration controlA person subject to immigration control is not considered as accessing public funds if it is their partner who is receiving the funds they are entitled to.
Child and working tax credits are claimed jointly by couples. If only one member of a couple is subject to immigration control, then for tax credits purposes, neither are treated as being subject to immigration control.
So you see Patrick, they'll be no issues at ILR application at all