If you are looking for an area to cycle in and have families who need entertaining as well, I can recommend this area as one to consider. Whilst it probably doesn't have the lure of Majorca, Girona or Tenerife for example, it is not a bad area for some warm spring cycling. There are some reasonable hills (e.g. Portman) in the area, the roads are quiet, in good condition and the Spanish generally overtake cyclists like a car and treat you with respect. That said traffic on the rural roads is very light so not much of a concern.
I found there are some excellent long straight roads which would appeal to time trialling types and the hills are decent enough to give the legs a work over.
If you don't know the area, there are group rides every Monday and Wednesday organised by www.bikinglamanga.com and you can hire bikes from Geoff there as well. I believe there are guides/triathlon coaches who he can recommend if that is your thing too.
If you are after some mountain biking, there is plenty of off road biking in the area and some of it suitable for youngsters too.
There is plenty of very reasonable accommodation in the area and of course the La Manga club is well set up for other sports as well (there's even an on site physiotherapist).
Temperature wise it is cool in the morning (might need arm warmers and a gilet) but as the sun rises, it warms up pretty quickly.
What worked well for me is that there is plenty of other activities to keep the rest of the family happy so if you are looking for a family compromise, it is worth considering.