A: same age as girls.
But your boys are the perfect age, and a lake is a generally an excellent place to learn.
Which lake?
Go with your boys and have a look and bit of a chat with the local windsurfers, they will give you the lowdown in your area.
second hand gear is hard to come by as it is normally snapped up quickly.
A rig kit with 2 sails ,a 2m and a 2.5m are about $400(sell for $300 after a year)Severne and ezzy make these.That would be the right size for both your groms.
Boards? Again near imposible to get a used 115 kids board.They are $1500 approx,but there are other options here.
feel free to PM me if you need any advice.
I made a big call in that thread a year and a half ago.
i also have a daughter who is 4
she will also be a windsurfer
she already knows she is going to be a windsurfer(brainwashing has begun)
she will be unleashed in 2 years time
she will be easier to teach,she is tougher than the boy!
Well its not 2 years yet and 2 weeks after Elli's 6th birthday she planed in the straps and that was using pseudo rig(ezzy).
Thats a year and a half earlier than her brother

She will from now on be using a proper rig,a power rig
SEVERNE XS-1start using little boards
and my final(timecomsuming)task of teaching her the waterstart,and my job is done.