Mojacar Playa Costa Almeria in Spain has miles of level promenade (called Paseo del Mediterraneo). There is the walk and the parallel bicycle lane. It is along the beach for miles.
Privately booked accommodation is readily available in the resort most of which would be within five minutes walk of the beach.
Eating out is excellent and inexpensive with a choice of Spanish, Argentinian, Colombian, French, Asian cuisine. The fast food outlets are there also. Even if you are not staying in hotel accommodation a weekly/fortnightly "all-in" eating menu is available there. However, I would not recommend it as the food (with good choice though) is the same every day.
If you want more difficult walks the near hinterland has everything from hill climbing to rock climbing. There are free childrens play areas along the beaches also. Mojacar Pueblo is 1.5 miles distant. It is a white Spanish village perched on top of a small mountain. Its streets are narrow and cobbled and there are extensive views for miles around. The local bus service is good and the fare is €1.20. Vera Aquapark is a short bus journey distant, but if you feel like the drive it will take around 15 minutes.
Access is through airports Alicante and Murcia directly from Ireland, but Almeria airport through the UK is probably cheaper. However, if kids are travelling you would need a direct flight.