I got my fingers very badly burnt by setting homework of this kind about 12 years ago, in my pre-child days.
What I learned after an army (well, nine, but they were marching) of enraged mothers descended upon me post research project set for homework is...
1- Don't be vague, be very, very clear about what you want the kids to do, which will also force you to be realistic time\scale wise about what you are proposing. Then you should be able to give them an idea of how long you want them to spend on it (eg 15-30 mins). Cos if you don't do that some kids will insist on working half the night for fear of being in trouble for not doing their homework properly.
2 - Teach the kids how to research first. Show them what you expect from them and how to do it because a parental interpretation of "research" is not always age appropriate and kids can end up frazzled with very exotic presentations and seriously grumpy mothers who have nearly killed themselves to give you what they thought you wanted.
3 - Don't assume a home has the resources you think they do. You risk compounding issues for kids who are already on an unlevel playing field. And one very upset parent will end up spending money they can't afford on an overpriced internet cafe with a very dodgy clientele and vent their resultant displeasure all over you.
4 - Don't assume the parents have the time to help the kid you teach to the extent you think they will. They may have other behomeworked kids, or demanding babies, and things like exhausting jobs, dinners to cook, a desire for relatively stress free family time after a whole day spent doing others bidding and a need to get everybody to a variety of sports\hobbies etc.. As fascinating as you find the topic in hand and your subject in general (being a bit one track minded) parents have a far wider range of priorities and juggling them is hard enough without you plonking another one on them. If you do plonk, they, being already rather stressed\tired, can take it very badly. And want blood. Preferably yours.
5- Act repentant. Grovel much. But assume they have no interest in their child's education in slightly snotty terms, inside your head only, for sake of personal safety. Have baby. Send him to school. Meet Nemesis. Repent again, but properly this time.
Don't get me wrong, I love doing project work with my son and my students. It can offer great learning opportunities and it's fun, not to mention gaining and honing various skills. However I find there is less gain and more pain when it becomes something they do AFTER a full day of education, rather than during it. Especially when it comes to the little ones.
I think a good rule of thumb is, if a project looks like a hassle to do in class cos it
risks being time consuming in practice
is hard to fit in a busy timetable
might not stay within strict timings and you could run out of time
brings up the question of dealing with making sure the required resources are available (and working properly\not being used by somebody else) for all
involves sorting out enough adults to supervise and lend a hand where needed
......... then probably it is going to be a hassle with similar issues in the home environment for a good number of the kids\parents.
And if it there aren't hassle\time consuming\busy timetable issue etc. etc. to consider, then why not do the research in class where you can provide uniform support and resources for all the kids ?
Where is the harm in swopping research projects with tasks that can be done independently (with resources from the school bag) and setting the latter for homework and making the former the classroom activity.
After all it's not like parents who enjoy doing that sort of thing with their kids can't take note of their little ones interests and get involved in doing research or projects with them if they want to on top of similar activities at school.