I've never stayed in Grindelwald but I have elsewhere in and around the Berner Oberland, so this may be helpful.
The good:- during ski season Grindelwald is as good an almost anywhere, better than many.
The bad:- late April is just about the worst possible time - I'm sorry to say - for visiting much of the Berner Oberland.
Late April is between seasons, too late for skiing - but you will likely have lots more success at your other base of Chamonix - and too early for hiking. There will either be still snow at lower altitudes in which case you will walk in slush - or if the winter is a bad as the one just past there may be lying snow - or if the snow has retreated from the lower altitudes the farmers will be muck spreading the fields. By muck, I mean all the cow manure that has built up over the winter, diluted with urine and water and put into tanker trailer, towed behind a tractor and power sprayed over the fields to fertilize them ready for the spring grass crop. It has a particular perfume which permeates everything. Maybe in Grindelwald you may be far enough away - or not - that it doesn't bother you at night.
Or maybe you and your party are from a farming area at home and will just breathe it in and congratulate yourselves on finding Swiss farming at its best. Your profile doesn't indicate city or country, or anything so we don't even know what country your party of 4 is from.
Also bad:- April is the month that usually one or more of the cable cars or trains undergoes annual maintenance to you may have to consider alternate routes if you are affected.
Also bad:- April is when a fair proportion of restaurants and businesses take their between seasons holiday.
Good:- Grindelwald and Interlaken are likely to be the least affected by April closures, unlike Lauterbrunnen, Wengen and Mürren.