Wow! I bet she wouldn't be saying this if you had a 1D series cam and all 'L' lenses.
JK!
If this were my wife, I would accommodate her this one time to see what type of shots or poses she likes. I would also take pictures of the children before they went, so I could compare and evaluate my own skills. If mine were 'better', then she might be happy to ask me the next time. If mine fell short, then I would learn from the other images and work on my technique or whatever element I was lacking.
The one thing you can't change is that you are 'Dad', and the kids will behave differently with you than with another photographer who is a stranger to them. He/she might be able to get some unique shots just by that alone. So, don't worry too much about it, you can never have too many pictures of your kids. Hopefully you both do a beautiful job with differing techniques so you can fill your albums with some nice images. The kids grow up way too fast, and this will be a nice way of memorializing them at their present ages.
In short, don't let this get you down, be confident in your ability to photograph and accept that their are others who have different abilities that might show a different side of the children. Just make sure you charge your wife for the pics you take too!



