Which resort? I am guessing either Arenal d'en Castell or Son Parc?
Either will be lovely, we first took our DS to Arenal when he was 4 - it has a gorgeous beach, is very, very pretty, a decent selection of good restaurants and bars, you can hire pedalos or kayaks. It's a perfect family resort, although is being quite hard hit by the all-inc hotels. If you are s/c then you will have a great time. If you are going all-inc please try to support the local community if you can.
If you are in Son Parc, then it also has a fabulous beach, but is much quieter than Arenal. Still has several restaurants and bars though.
The north of the Island is more hilly and greener than the south.
I would really recommend hiring a car - Menorca is tiny and only takes 30 minutes to travel from the North coast to South by car, and 45 mins from Mahon (the capital) in the east to Ciutadella (the old capital) on the West coast. Both of these towns are well worth a visit. They are authentically Spanish, have fabulous architecture and plenty going on.
Depending on what time of year you are going, there is bound to be a fiesta happening in one of the many towns and villages.
There are a plethora of Stone Age villages and burial sites you can visit, some of which are very interesting.
The town of Fornells is also on the North Coast and is an idyllic fishing village, has a brilliant fiesta the 4th weekend in July and is well worth a visit any time, lovely harbour / walks and some fantastic restaurants.
Also worth a visit are the lighthouses of Punta Nati, Cavalleria and Favaritx. Quite stunning visually due to the coastal scenery.
This website has lots of useful information :-
www.menorca-net.co.uk/
Enjoy and let me know if you need more info. I will be back for my 11th year running on 19th July.