I don't get all this OP bashing. She is a mum - like the rest of us - who is anxious about her child going on a relatively long trip without her. OK this is aibu, but can we not be a little more sympathetic whilst still giving the same advice? Blimey there are a lot of people on this thread that must be getting strangled by their judgey pants.
Victoria48, I totally understand why you are worried and fwiw, I think its natural for an awful lot of mums. Reception children are still very little and letting go and allowing your dcs to do things that you might worry about is always hard.
I am similar to another poster up thread, in that my eldest has ASD. He hadn't been diagnosed in recption year and I remember being absolutely petrified of him going on school trips at that age, as I was for ds2 who doesn't have ASD and will be for dd when she starts next year.
All sorts of horrible possibilities were whizzing around my head, but I had to try to get it into perspective for ds's sake. Our school does always take some parent helpers, but it's always the same parents that get chosen (but that's another story) so I wasn't able to go myself.
In reception year our dcs were taken to a certain small children's theme park and I was a bit 
about why, but, if I hadn't allowed ds1 to go, he would really have missed out on such a lot of fun, as well as things like paying for his own souvenier (sp?) in the shop etc. As it turned out, the trip was linked to the classroom reward system and they had earned the trip through their good behaviour all year. If ds hadn't gone, it could/would have given him the message that he hadn't been as good as all the other children.
I paced the house the whole day of the trip and was the first one there to meet the coach when they got back, but I needn't have worried - he had a blast and still talks about it now. He spent the whole day with another lovely parent who looked after him as if he was her own, which was no mean feat given that he had undiagnosed autism. He felt safe and secure the whole day and was under constant careful supervision, as were all the other children.
Ds1 also gets travel sick, but the staff are well aware that they will have a number of children who get it on every school trip, so are clued up on the best places for them to sit on the coach and have a number of tricks up their sleeve to deal with this.
I was actually able to go on ds2's reception trip (to the sealife centre - they were studying the sea at the time 
) and have been on a couple of trips with ds1 since his diagnosis and I can promise you, school have so many rules and procedures to follow for school trips that the children are really taken care of.
Ds is now 10 and last year we had to face letting him go on a weekend outdoor adventure weekend. He said he didn't want to go at first, but once the rest of his class started talking excitedly about it he was drawn in and got really excited. Then when it came to the actual day he was really scared and didn't want to go. Tough one, because neither did I really, but I didn't let him know how worried I was and we talked through his worries and dealt with them. He went and had an amazing time, in fact the staff accompanying the trip all said they thought he got more out of it than the other children.
There is another one coming up in September, but this time it's a whole week away. Ds isn't sure if he wants to go, because although he seriously loved the last trip, he's worried about being away from his family for so long. We have had to take the decision to pay for it anyway, as he really couldn't decide. I am already fretting about this trip, there are lots of activities which could be potentially dangerous for my ds, lots of water sports (he can't swim and has motor co-ordination problems) but I have to trust that the qualified centre staff know what they are doign and that the school staff will really take care of him. I am pretty sure he will decide he does want to go at the last minute and of course I will let him go, but I will definitely have a sleepless week. If I stop him going, it will just mark him out as even more different than his peers and means he will be left out for weeks after they come back and are full of all the things they did on the trip.
He has gained such a lot from his school trips, it's helped him to have something in common with his peers, which is so important for all children, but even moreso to a child who struggles socially. It's given him a safe way to be a little more independent of me than he usually gets to be and encouraged him to face his fears and realise that he can do things he never believed he could.
Ultimately, it's your choice. If you don't feel your ds is ready, you are better placed than anyone else on this planet to know that and no-one can tell you otherwise - BUT - you need to be completely honest with yourself and if it is your own fears that are the problem, then from my experience it is worth biting the bullet and letting him go, as they really do gain such a lot from these trips, even if they don't seem at first glance to be all that relevant to school/education.