I need to travel from London to the north and my children aged 5 and 8 will join me on the train at Milton Keynes, delivered there by their grandparents. If I book the ticket for all three of us from London it works out cheaper than a single for me from London to MK and then all three from MK to destination. But is it possible for the kids to join at MK if their ticket is from London, or will it cause problems going through the barriers and boarding at MK?
It depends on the fare type.
If this is an "Advance" ticket - an inflexible ticket which requires you to travel on a specific train - then this is not, in theory, valid. There is, of course, the possibility of station staff taking pity on you, but it's not something you should rely on.
If, on the other hand, you're buying flexible tickets - (Super) Off-Peak or Anytime Singles or Returns - this would almost certainly be valid, but I'd have to know your destination to be sure (a few destinations have "break of journey" restrictions on the fare, specifically ones in North Wales).
Other things to consider:
- I assume you're travelling Avanti West Coast and want to ensure you sit together? If so could you book through their own website and specifically choose your seats? Not sure how COVID affects this ability though. That way you could buy a single London-(Destination) for yourself and two child singles Milton Keynes-(Destination) for your kids. If all else fails, due to COVID social distancing you should be able to book a table seat for yourself (if one is available) and then have your kids sit with you, even if they have reservations elsewhere on the train.
- If the worry is because you're actually using a Family and Friends Railcard, bear in mind that this is not valid if you're not travelling with kids, so your London-Milton Keynes portion would be invalid, even if you have also bought child tickets (if you don't physically have children with you, it's not valid). In this case if you want the discount your only option is to do as you suggested - a ticket London to Milton Keynes, then three tickets Milton Keynes-(Destination). If you're not considering a Family and Friends Railcard, this is something you should be considering - they cost £30 for one year or £70 for three, and give you 1/3 off adult tickets and 60% off child tickets for up to 4 adults and 4 children, as long as one of the (up to two) named cardholders is travelling along with at least one child. If you make regular rail journeys with your kids this is almost certainly worth it; and depending on how much you intend to spend sometimes it can be worth getting it even for just one journey.
- If you're travelling London Northwestern Railway they don't offer seat reservations so this should not be a concern.
- Make sure their grandparents leave plenty of time at the station, as there are ticket barriers at Milton Keynes Central. I'm sure that once the situation is explained they will be let through, or at the very least the children can be handed off to a member of staff who will see them safely onto the train, but I'd want to avoid any last-minute dashes for this reason.