If you are just worried about keeping warm until serving (no traveling with them) you might want to try simply placing the pot with the mashed potatoes in in a larger pot (or roasting pan) on the stove and filling the larger vessel with a few inches of hot water and keep on a low simmer. The water / extra pan should keep them from scorching until you are ready to serve them. Seems to work well for me...

I'm having approximately 30 people over for a Christmas Eve dinner. There's no way I'll be able to have all lobsters coming out of the pots at the same time...more likely two separate batches about 15-20 minutes apart, which leaves me wondering what to do with the first batch. Has anyone had any luck with keeping lobsters warm in a steam tray for half an hour or so? I'm concerned they will dry out or become rubbery / over-cooked. Any thoughts / suggestions? Thanks very much for any advice!