When Choosing a Bed I believe it is worth investing in the mattress.
Go for a large a size as possible.
5ft at least for a couple.
Latest technology is Memory foam - which can feel a little different but does provide good comfort
My recommendation is for a combination mattress, traditional pocket springs with a memory foam top layer. You can get a sprung divan base to go with the mattress. this improves the life of the mattress but adds to the cost. Approx €1200 to €1500 for the above type bed.
The kids soon grow out of the theme beds, go for a good quality traditional bed, you can decorate it with duvets. But in a few years it can be used normally.