What part of Tenerife are you thinking of going to, 3* 4* 5*? There are loads to choose from in Playas Americas/Fanabe/Adeje that I can recommend. Maybe other ABs can recommend some from the North at Puerta del Cruz
From memory though I don't think there are proper beaches in the North just man made type. Los Christianos would probably suit children better than the next door noisy resort of La Americas (we didn't like it) but we went years ago and there are some newer resorts along the coast now which would probably suit families better.
We went to Bahia Pricipe last year and it was the best holiday/hotel we've ever had, it's a little way out but buses are every half hour from the top of the road. My brother went to Bahia Princess in Fanabe and said that's excellent too. We loved Tenerife, going back next year.
Playa de Las Americas has everything you could possibly need. Los Cristianos is quieter, but you can easily walk to Las Americaas from it. or a cab ride costs hardly anything. Hotel Las vegas in Puerto de la Cruz is very good too.
We are stopping at the H10 in Americas week after next I.L.S. If you pick up H10 In the brochures or trip advisor you cannot go wrong, we go there often, Los Cristianos is good & again there are many good hotels, if you pick one check Trip Advisor. 20mins from airport.