Never really considered Morocco for a family holiday, but I tend to do a four day break once a year by myself so that has possibilities. I maybe do Morocco (and Tunisia) a disservice, but they don't look particularly enticing for a family holiday. Though some Morrocan mountain resorts look stunning but as you say not much for kids to do.
Personally I would avoid Agadir although it is the most straightforward way to take a family there.There are very reasonable package holidays for families with Thomsons and Thomas Cook.
One or two of the hotels get good write-ups on Trip Advisor.
Once there you could hire a car for a few days and easily get to the famed wetland site further south, ?Massa[forgotten the name]
If you follow the signs for the airport the world is your oyster once you drive past it.
The road is straight and not busy beyond there.You can get to the Sous Valley and the Taroudant area which is full of birds.
They use irrigation troughs around the farming margins of the town which are a magnet for birds.
From there you can head up towards the Tizi nTest towards the Atlas mountains which is a wonderful route to stop and see birds along the way.
If you don't fancy Agadir there is an atmospheric old hotel in Taroudant called the Palais Salam.
We stayed there with our family when they were young.There are two lovely pools there.
It is set within the red walls of the town[google it to give you some idea]
We stayed half board and the food was excellent.
The advantage is that you can do your birding on foot:there is a great park just outside the hotel full of birds.You can also walk to the edge of the town where there are orchards,irrigation troughs and rubbish dumps.Great for birds.
Also the hotel hired out bikes so you can have a good look around the farmland and local villages.
Otherwise hire a car for a few days.From here you can easily reach the Atlas mountains north along the Tizi n Test or south to the Anti Atlas.
We kept on stopping every 5 minutes as there was always some birds of interest around.
Just north of Taroudant there is a road towards Amcherk which you can either walk cycle or drive.It has small farm fields and hedgerows so its really attractive for birds.
If you did it DIY you could probably get a cheap flight to Agadir then either get a taxi to Taroudant or hire a car from the airport.Taroudant is only just over an hour from the airport.
Essouaria is a different kettle of fish but would definitely suit a family holiday.
The advantage is that you can do your birding either ;on foot,petit taxi for short journeys,shared taxis for longer trips or by bus.You don't
necessarily have to hire a car.
The centrepiece is the old walled town and the magnificent sea fortifications.
A huge wide beach sweeps south and there is a promenade which runs for miles.
The fishing harbour is a magnet for gulls : Auoidan and Slender Billed Gull are commonly seen
It is very laid back and nobody bothers you here.
There is a river estuary near Diabet about 2 miles south.
I used to get a petit taxi from the hotel[cost about £1] and every day new migrants were arriving every day on their way north.One day there would be a flock of Spoonbills[11 seen one day] the next day they would be gone and replaced by a gathering of Black winged Stilts.It was a great area for passing Wheatears,Sub Alpine Warblers,Woodchat Shrike,Moussier Redstart,Dartford Warbler and Great Grey Shrikes amongst other birds.
There is a great birdwatching area at Sidi Kaouki which is a beach backed by a woodland area[Moussiers Redstart].
A regular bus service goes there every day via the airport or you can get a shared taxi.
There is another great birdwatching area just north at Moulay Bouzerkton reached by a straightforward road.
The only problem with Essouaria is that the road from Agadir is unlike the normal French Legionaire built ramrod straight roads-it is long and winding.
You would either have to hire a car or arrange some sort of transfer from Agadir[you can reach it from Marrakesh by bus]
Ouarzazate is yet another different birding experience.The hotels are great and would suit a family holiday.The only problem:it is a 6 hour drive from Agadir!
Most Moroccan birders tend to drive for hundreds of miles sweeping up the rarities.
Basing yourself in one place is far more relaxing and would suit a family holiday.
It is defintely a wonderful place to go to especially in Spring when thousands of birds are passing through on their way north.
I think you saw my report on Mahdia in Tunisia.
This place really surprised me especially the huge salt flats at Sebkha Moknine and the wonderful habitat on the edge of the town.
All your birdwatching can be done on foot,using the excellent local train or taxis.
The Riu el Mansour was the sort of hotel we normally avoid but it turned out to be better than expected.
Rows of sunbeds around the pool and animation teams.
We plumped for a room at the back of the hotel which was the saving grace.All the sea facing rooms actually face the rows of tanning guests and the animation team nonsense.The rooms at the back[non sea facing basic rooms] were not only cheaper but also completely quiet and peaceful.
This would definitely suit a family holiday without breaking the bank[Thomson Holidays].
The food was good quality and the staff were really friendly and helpful.