There's the production type called "mixed recording" that is very common in film music productions and used by many composers out there.
There's the possibility to prepare the "mockup" on your computer and then in studio you record over it the live music. That requires that all musicians need headphones. They have to hear the signal from the sequencer (because of intonation reasons) and a metronome click that it's definately in sync.
Or I heard of a professional film composer that there's also another possibility that is very much used in film music because of budget reasons it fits perfect to your situation.
In case of having only a small orchestra available there's the possibility of making "overdubs" within each instrument groups.
For example if you have 2 contrabasses they can easily record (along to the prepared sequencer tracks) the bass parts and then record the same part again. You have immediately the sound of a 4-head bass group or if you do the same again and again 6 or 8 basses.
The same with the cellos, violas, violins and you've a full string orchestra group that sounds really powerful. Then you can go on with the brass and the woodwinds. But it is very important this way to start always with the lowest (bass) instruments and then the higher instruments. Otherwise you can get serious problem with the intonation! And don't forget to make click tracks (not only for rhythmical parts, also and especially for free, rubato passages!)
There are 3 advantages in this way of production: You spare money, you can reach (especially with a very rhythmical music) rhythmical precisio, you will have a clean intonation and have lot of possibilities when it comes to mixing (as you have all the tracks seperate and dry).
The 3 negative things: for example the oboist has never really played together with the violin, so in a way it will never have that same kind of "depth" (both as a sound and on the emotional side) as a real large symphonic orchestra.
Another advantage is that you can decide later easily which sound source you prefer to use or you can mix them (for example: if the intonation of the live cello is not that good for a moment you can easily control everything and for example fade in the sampled cellos, and so on...) That's really an interesing way of working and with a little luck you'll be very happy with the result.
That way of recording is really very much used nowadays (not only in Germany, also in big Hollywood productions).
I wish you all the best and I'm interested to hear your experience!
Best wishes,
Andie