We have camped at Easter a fair bit. It's a little bit earlier this year than some , although it doesn't always make a difference with the weather chances.
We would always have an EHU with an Easter camp (but we also tend to go for 7-10 days). We have a cheap fan heater with 2 settings which has run fine on most EHU camps. Ours has an automatic cut off if it gets knocked over. It's pretty much instant heat when it's switched on but we don't use it over night. I know some people have an oil style heater which would take longer to get to temp but would be less noisy and perhaps safer at night? Don't forget you might find you need more lighting options too for the evenings- you are less likely to be outside your tent looking at the stars.
I would also make sure you pack good sleeping bags/mats, and layers of clothes with woolly hats/gloves/slippers etc. wrapping the body so that it is warm makes the real difference here. Take a few more bits of quick and easy heat food that warms a tummy- porridge, custard, cup a soups, noodles etc.
I also chose campsites differently for the colder times- perhaps better bathrooms that are heated and like a PP said, a site with facilities. If they're not usually your thing they are normally much quieter at Easter. Also think of what you might do in the day- are there enough wet/cold weather options.
In spite of the challenges, it has been a favourite time of mine to camp. I'd always relished the prospect of getting out in nature again after long winters, and one of my favourite memories is crunching across frosted grass in the morning.