Keep an eye on the weather, it might be good, it could be awful with Gale force winds ,there will probably be snow cover. Ill see if I have some old photos. I have been up in April and couldn't make the top because of the wind conversely I have been up in Oct/nov and had a superb day. It's really too early to tell. In relation to the terrain from the approaches up from the ski car park the gradient is such is that you won't use an ice axe unless you veer off course, and the walk across the plateau is fairly level where your problem may be navigation should the cloud be down and the wind blowing. The final ascent up Macdui is gradual and as I say you may not use the axe but it should be carried in case of difficulties. The crampons or kahtoolas will be useful depending on the ground cover. A walking pole will be a good addition. Are you doing Cairngorm as well in a walk back across the plateau