I don't have any musical background or ability; can I still help my child practice?

Yes, I think anyone can help their child practice, what you can't do is try and teach them. You can help them to understand things that are taught to them - teaching an adult is easier than teaching a child sometimes just because the adult understands more what is being said but doesn't know how to do it, so see if you can simplify things that don't make sense to your child.

You can also help them by encouraging them and giving them positive reinforcement when they practice so that it stays as something they enjoy and doesn't become a chore that they hate. You can listen to them and ask them if they need anything i.e. more lessons, a coach or just a simple drink of water, just be there for them and whatever you do don't upset them or make them self conscious when they practice, don't ruin their confidence. If something is clearly not right (people with even no musical training know when something sounds awful) tell them gently.

People think in order to help their children they have to teach them how to do it but that's not the case, just support and love them unconditionally.

I wish you and your musical child all the best

Sure.  Help them make practicing part of an every day routine.  Don’t dictate a specific amount of time that must be spent practicing and you can allow some time to “play” and experiment with the instrument as well as more serious practice.  The point would be to make spending some time with the instrument every day.

Set practice goals and don’t be afraid to offer rewards.  Goals should be specific and achievable during a practice time.  So break bigger goals into smaller daily goals.  For example, instead of rewarding only if the memorize an entire piece of music, set the goal that I’d they can play 6 measures with no mistakes they get a small reward or token.  Then they can keep building on those past accomplishments.  Maybe they can save up tokens for a bigger reward.

Don’t yell at them about playing or practicing and don’t use practice as a form of punishment.  Be enthusiastic and engaging.  You can get creative in motivating them to practice - maybe making practice some type of “game”.  I remember my mom (who was not musical) would count how many measures I could play without mistakes and then she would do that many sit-ups.   (I played the violin ).  Look through the internet for some other possible suggestions.

Good luck 

You could encourage said child.  Then find a suitable teacher.

Unless you really are tone deaf, you should be able to.