That is not right. You add 2 inches to one of the legs of the rake&trail triangle and it is going to affect the geometry. No way around that, add 2" to one side, the other 2 are going to be different. Will it affect it adversely? It might, it might not.
Read this; http://www.rbracing-rsr.com/rakeandtrail.html
I did exactly what you are describing for about 6 months (2" extensions on the stock trees) and about 2000 miles - but I still had the 19" wheel, tho.
It ends up increasing your trail since you've leaned the bike back and effectively increased the rake of the neck a couple of degrees. You can feel the difference in the corners - it takes a bit more countersteering pressure to hold the bike in a bank as the bike kinda resists being turned a bit and wants to go straight. But it is not a very large difference. If you like to ride at freeway speeds, you'll really like it - as the bike rides on rails - stable as a truck in a straight line.
If you like to zig-zag through the twisties, then you probably won't like it - but if you ride it like most people ride cruisers, then you won't mind the subtle change in handling a bit.
I used to have some pics of my bike with the extensions on the stock trees but I've since deleted them (I have 6* trees now).
You have done two things to slow the steering down: put the 21" front wheel on and the 2" fork extensions. You would be running about 7 1/2" of trail, great if you want to go in a straight line, not even safe in the twisties. I'm not just plugging my product (maybe a little) but raked triple trees will correct your trail to a very fun 4". Great in the twisties and plenty stable in a straight line.
Allow me to revise my earlier post in response to all the rocket scientists on this board...
Adding two inches to the forks without changing anything else will in fact change the trail an insignificant amount and will therefore change the ride characteristics to such a degree that you may not notice the difference, ever.