As a parent whose DS wants to take the exam in 2019, and that's the key. He wants to do it. We have made our DS realise the demands in terms of time,commitment and skill requirement.

We certainly don't want to 'hot house,' our DS, so I'm looking for strategies to make the lessons as fun as possible.

Always start with a game.
Have a timetable for the week so each day is different and tasks at this stage aren't too long and tedious.
I already pair read and discuss the texts.
Discuss vocabulary.

And we ensure he does all his extra curricular activities. Football including his matches, martial arts,friends etc.

Any other suggestions for strategies that have worked?

How many sessions a week are you planning? Every day is far too much.

I agree, always have at least 2 days where you do not speak about the 11+ - we all need a break, reading is ok.
What worked for me was little and often, I also gave my DC the choice of what they wanted to do that day, if I felt they had not done so well in, let's say, comprehension, then I would suggest we go over the mistakes and try a new one but if they really did not want to do that then I would not push.

We made an effort to use tricky or new words in our conversations.
A treat if they have done really well goes down well and acts as a good motivator.

A rigid timetable just did not work for us but may work for others, I found keeping it very lighthearted was the key.

I agree.

There are more than 2 days where it's totally impractical to do any studying anyway. Our DS has football,martial arts etc,cubs and we couldn't fit it in.
We don't want to spoil any of the EC activities.

I like the tricky words...