Actually it makes perfect sense Mummachicka

.
If you put a blind behind the sheers I wouldn't put it in the recess but in front of the window. That will prevent light peeking through the sides of the blind. Also if it is a roller blind set it up so it pulls down at the back not the front of the roller. It keeps more light out. Little ones wake early enough without sunlight helping

. I love the sheers or pink drapes idea.

I am so proud of you tackling the chair

. Is this your 1st craft project?
So this is what you do:
Make sure the foam is cut to the size of the board.
Use something like liquid nails to glue the foam to the board for the seat.
Buy some wadding from Spotlight. You need enough to cover the foam and wrap under the board.
Wrap the wadding over the foam and around the edges of the board. Glue the wadding underneath the board. Cut away any excess in corners.
Position your fabric. Consider any pattern when positioning. Use a staple gun (about $25 from Bunnings). Put 1 staple in the centre of each of the 4 sides. If you make a mistake the staples are easy to remove with a normal butter knife. If happy continue to add all the staples but leave the corners - also don't staple too close to the corners at this stage.
The corners are the most difficult part. You can try to do a mitred corner like a hospital bed corner. Or you can spread out the gathers evenly on the corner. It is really about fiddling to get it to what you want. When you are happy staple the corners. Then cut away excess material to the board.
The board should be able to be attached to the seat as it was originally.
I hope this helps.