Matthew has a very similar routine to your lo, bath 6.30 bottle and bed at 7pm and we used to stick to that where ever we were, now matthew is that bit older i find that when we go out for the evening like to my mums for tea i give him his tea at 5pm as usual but hold off his milk till we are back home as he settles much better if he has his milk just before sleep. We tend to take our high chair to my mums and give him healthy snacks to keep him entertained whilst we eat. In the early days of doin ghtis we did take a bottle with us just in case but very quickly he adapted to this.
Try not to worry about his routine too much, i know i used to but they seem to manage with the odd night out of the routine and when it comes to changing it, it's not like it's going to be one great big jump from baby routine to 3 year old one, it's gonna happen gradually over time.
hope this helps
Claire x