if you plan to be at the beach all day this is a good idea, however it will probably only work if your child is already used to having playpen time at home otherwise they might not like this new idea of being confined. We use the pack n play though for time up out of the sand a play yard that is on the sand you might as well let the baby roam. Both of my daughters had/have some alone playpen time everyday and actually enjoy it. I also use it(pack n play) for naps on the beach (my youngest is now 12 mos)try to bring a light weight blanket to cover it with to help make it a little darker (leaving room for fresh air to circulate in the screen sides) and of course keep it under the umbrella. I only use it when my baby needs a break so make sure to give baby plenty of time to explore the sand and play. The best thing to do is either rinse baby clean then dry new diaper all that b4 putting in playpen that way its a break from the itch sand and baby can sleep or play comfortably. small baby pools are great a 1 ring blow up is fine for this age it can be refilled and cleaned easily plus its easy to cary. Be prepared though some babies arent gonna last more then a n hour or so at the beach my kids and I go all the time but if they are not used to it sometimes nothing works.
As far as the hotelyou may expect the scheduel to be a little off we have had it go 2 ways either the baby was so tired from all the fun activities we had going on that she slept great no probs (you can darken hotel rooms easily ) so darken for a nap put on white noise and I say go on the balcony w/ a book or some cards ect or if there is no balcony 1 of you go get some take out and have your own mini picnic in the hall, or enjoy a nap yourself. if your lucky at night the baby might be able to sleep even w/ the tv on if not be prepared for an early night, we usually keep the bathroom light on and turn the tv volume down then turn it off turn off rest of lights and pretend to be going to sleep yourself, so once the kids are really asleep we can turn on the tv and slowly adjust the volume LOL. Its sure not like vacations b4 kids but fun all the same, also once the baby is asleep you can try putting a blanket over the pack n play to block the light and then turn the lights on just b sure to take the blanket off b4 you go to bed. Or you could always have a little romance if you must stay in the dark, your baby wont know the difference ; ) Oh I thought that bathroom as a bedroom idea was great too just read that!